Current disease treatments for the ornamental pet fish trade and their associated problems

The trade in live ornamental fishes to be held as companion animals or displayed in public aquaria has an estimated global annual value of US$15 – 20 billion. Supply chains for ornamental pet fishes often involve many more parties than for fish farmed as food fishes, and at each stage, fishes are exposed to stressors including handling, confinement, crowding, mechanical disturbance, and poor water quality. If chronic, these stressors can compromise their immune system, making fishes more susceptible to pathogens. Mortality and morbidity from infectious disease can result in considerable welfare impacts and massive economic losses for the industry, and the range of infective agents seen in ornamental species is well documented. However, treating these diseases is not straightforward with practices varying greatly across the trade and with several approaches having unintended consequences, such as the emergence of resistant strains of pathogens. While disease treatments for a handful of fish species (e.g., koi, goldfish) have received focused research attention, for the home aquarium owner, there is an increasing reliance on products based on natural compounds which have received far less scientific attention. This review aims to highlight the gaps in our knowledge surrounding the range of disease treatments used across the ornamental pet fish trade, with a particular focus on freshwater tropical species destined for home aquaria. Consideration is given to the potential problems arising from these treatments, including microbial resistance and effects of treatments themselves on fish health and welfare.


| INTRODUCTION
The trade in live ornamental fishes to be held as companion animals, and their associated products, represents an economically important global industry.2][3] The global ornamental industry relies on transnational supply chains to provide fish keepers in countries such as the United Kingdom, United States, and Germany, with fish reared/ collected from nations such as Singapore, Israel, and Japan. 4,5These supply chains involve many parties including importers, exporters, distributors, wholesalers, and retailers.At each stage in the supply chain, fishes can be exposed to a variety of stressors which can result in mortality. 6These stressors include handling, confinement and crowding, 7 mechanical disturbance during transit, 8 poor water quality, accumulation of toxic waste products, and reduction in dissolved oxygen. 9Exposure to stressors over a period of time can compromise the immune system of the fish making them more susceptible to bacterial diseases. 10In addition to the effects of long-term stress on the immune system, fishes are routinely netted for grading or preparing for transport which can result in loss or damage to the epidermal mucus layer that protects fishes against pathogens. 11,12sceptibility to disease is therefore a major challenge for the ornamental pet fish trade and is the second most frequent cause of ornamental fish mortality and morbidity, after collective water quality issues. 13These mortalities result in economic losses for the ornamental fish industry 14 and an overreliance on antibiotics has fostered resistant strains of pathogens. 15Treating these diseases is not straightforward, and research has focused primarily on one or two species.Although the majority (95%) of freshwater pet fishes are tropical, research into ornamental fish diseases is most advanced for cyprinid species (e.g., goldfish, koi) where development of a vaccine for koi herpesvirus disease (KHVD) looks promising for the industry. 16However, for small freshwater ornamentals, destined for lives in home aquaria, far less scientific consideration has been given and more effective treatments are needed to prevent disease.In many importing countries, there is an increasing reliance by home aquarists on products based on natural compounds, potentially due to their perceived environmental sustainability (Arapi EA, Cable J. unpublished data).However, these disease treatments have generally been overlooked within the scientific literature and their efficacy and effects on general fish health and welfare are under-researched.
Here, we review disease management strategies within the freshwater ornamental fish trade with a particular focus on tropical species destined for home aquaria.We look first at more traditional approaches such as the use of antibiotics and the emergence of antimicrobial resistance (AMR).In the second part of this review, we present a systematic review of information available on treatments available to home aquarists highlighting the gaps in our knowledge surrounding the range of disease treatments used across the ornamental fish trade and areas for future research.

| DISEASES IN ORNAMENTAL FISHES
Infectious diseases cause significant mortalities to stocks of ornamental fishes, including in aquaculture and research facilities, sometimes resulting in cumulative mortalities >50%. 17,180][21] While these outbreaks are undoubtedly costly to the industry, data on the direct economic impact of infectious diseases within the ornamental trade is sparse, not least as there are few incentives for fish farmers to report disease outbreaks in countries without a legal obligation to do so, and where reputational damage could occur.
Ornamental fishes are susceptible to infection by a plethora of microorganisms including metazoa, protozoa, bacteria, algae, fungi, and viruses.Many diseases are caused by Gram-negative bacteria which are ubiquitous within ornamental fish holding water and can opportunistically infect immunocompromised individuals. 22,23ere is considerable overlap in the environment favoured by many ornamental fish species and that required for bacterial growth (e.g., warm temperatures, high concentrations of nutrients, and good oxygenation). 23,24There are also some notable protozoan and fungallike diseases that commonly occur when the immune system of ornamental fishes is compromised.While viral diseases are an issue for ornamental fishes, prevention of viral diseases generally relies on maintaining virus-free breeding stocks, vaccination where available, and good biosecurity including disinfecting setups between production cycles, UV sterilisation of water, and implementation of sufficient quarantine periods. 25There is an extensive literature on KHVD and a commercial vaccine available in some countries. 16However, for the majority of tropical freshwater fish that are traded to the home aquarium owner, there are no commercial chemical treatments for viruses; therefore, viruses are not explored in great detail here.(mycobacteriosis) and Nocardia spp.can appear weakly Gram-positive but also present as an acid-fast bacterium.

| Bacterial diseases
Many of the bacteria summarised in Table 1 can cause tail/fin rot in fishes. 86,87This occurs when bacteria colonise the fin tissue and cause necrosis and degeneration, often unevenly, giving the fins a ragged appearance. 13,22Poor water quality and fin damage due to aggression or inappropriate handling can predispose fishes to fin rot. 88In severe cases, the fin can be significantly reduced, and the infection can progress to the body surface. 88,89Fin rot can compromise the commercial value of ornamental fishes destined for home aquaria, particularly in species prized for their long flowy fins, for example, fighting fish, Betta splendens.

| Parasitic diseases
There are numerous parasites, which present considerable economic and welfare-related concerns to the ornamental industry from a diverse range of taxa including protists, monogeneans and T A B L E 1 Summary of the main diseases reported for freshwater fishes held as companion animals in home aquaria.For more detailed reviews that include gross signs of common diseases, see Cardoso et al. 14 crustaceans. 64,90,91Some common parasites for pet fishes are Piscinoodinium spp.(freshwater velvet disease), Icthyophthirius multifiliis (white spot disease), skin and gill flukes (Gyrodactylus and Dactylogyrus spp.), and roundworms (e.g., Camallanus and Capillaria spp.).Freshwater velvet disease is caused by the dinoflagellates Piscinoodinium sp. which have a direct life cycle with three stages lasting between 4 and 15 days. 59,84Stage 1 is a free-swimming dinospore which attaches to the epithelium of the host's skin or gills with a specialised extension known as a rhizoid.Once attached, the dinospores become trophonts (feeding stage) which actively parasitise upon the host's cells.Finally, the trophonts detach, encapsulate themselves, and turn into tomonts (reproductive stage). 592][63] Motile theronts (infective stages) of this parasite burrow into the epithelial tissues of the skin, fins, or gills of the host fish where they transform into spherical trophonts (feeding stage) and feed on the surrounding tissue. 60Two genus of fluke (monogenean) which are particularly prevalent in the ornamental fish industry are Gyrodactylus and Dactylogyrus.The former reproduces viviparously while the latter are oviparous. 92,93gardless of reproductive method, they have direct life cycles and relatively short generation times leading to rapid transmission between host fish. 93Using specialised hooks they attach to the external body surfaces including skin, fins, and gills (favoured by Dactylogyrus spp.) feeding off the mucus and epithelial cells of the host. 94,95 terms of endoparasites of ornamental fishes, perhaps the most significant are nematodes, specifically Camallanus and Capillaria spp.
Both species are similar in clinical presentation, both targeting the gastrointestinal tract of the host fish. 78However, Capillaria spp.have a direct life cycle whereas Camallanus spp.typically uses an intermediate copepod host, although they have exhibited flexibility in this regard directly infecting fish. 76,78,96

| "Fungal-like" diseases
Aside from microsporidian parasites, diseases caused by "true" fungal pathogens of fishes are relatively rare 84 ; although rare Aspergillus, Rizopus, and Mucor have been reported to cause disease within ornamental fishes. 97,98Of the microsporidia, two species commonly infect pet fishes-Psuedoloma neurophilia and Pleistophora hyphessobryconis, the latter being the causative agent of "neon tetra disease," despite being nonspecific to neon tetras and infecting a broad range of fish species. 99,100These diseases present a particular problem for zebrafish used as model organisms, as they often have subclinical effects on behaviour which can confound interpretation of behavioural endpoints. 99,101,102r fish destined for ornamental purposes, these diseases represent less concern, typically resulting in subclinical effects with mortality only in some chronic cases. 99,103Additionally, there is no proven treatment for either pathogen with evaluation of treatment options in its infancy and current guidance to euthanise severely infected fishes. 104Therefore, these diseases are not considered further here.
Diseases caused by the fungal-like oomycetes or "water moulds" (e.g., Saprolegnia, Achyla, and Dictyuchus spp.) are relatively common in freshwater fishes in part due to their low host specificity. 81They are ubiquitous within aquatic environments and typically cause secondary infections, opportunistically infecting lesions caused by parasitic or bacterial diseases. 84Alternatively, they can infect hosts by colonising physical trauma caused by aggression or inappropriate handling. 83Poor water quality and stressors such as crowding and unsuitably low temperatures seem to increase the likelihood of infection. 82,84,85Fish eggs are also at risk of infection from oomycetes.By initially colonising dead eggs, water moulds can spread to healthy eggs, which they could not otherwise colonise, and can cause extensive egg mortality. 105,106| DISEASE MANAGEMENT

| Transboundary spreading and zoonotic potential
Within the ornamental fish industry, live animals are transported on a global scale in substantial quantities and whenever live animals are transported from one location to another there is opportunity for cotransport of pathogens. 107Therefore, a key aspect of disease management is risk consideration for the spread of pathogenic organisms.
Additionally, while ornamental fishes are destined to spend their lives in captivity, escapes or intentional releases can pass on pathogens to naïve natural populations through a process known as transboundary spreading. 108,1091][112] This is typically an issue with cold water ornamental species (e.g., koi and goldfish), as many countries importing ornamental fishes are located in temperate regions where tropical species are less likely to survive on release.However, some typically tropical species have been found in temperate regions, 109 and rising global water temperatures may increasingly exasperate the problem.
Humans are also susceptible to transboundary spreading via fishhuman zoonoses.In 2012, a systematic review of ornamental fishhuman zoonoses highlighted Mycobacterium marinum as the greatest cause for concern, with at least 32 recorded case reports (single occurrence of human illness) and 16 case series (two or more occurrences of human illness) of human M. marinum infection linked to ornamental fish exposure, including potential links to three deaths in immunocompromised individuals. 15Other cases have been reported since, 113,114 and a more recent review found strong molecular and epidemiological evidence for zoonotic Mycobacterium transmission. 115uthier 115 also highlighted three other zoonotic pathogens (Clostridium botulinum, Streptococcus iniae, and Vibrio vulnificus).However, these were more related to consumption or handling of food fishes, with little relevance to fish kept as pets.The true extent of humanfish zoonoses is likely underestimated due to limited awareness and monitoring/surveillance. 116,117 For example, infection by Mycobacteria marinum, is not notifiable in most countries. 116,118Due to the relative frequency of exposure, professionals within the ornamental industry are most at risk from zoonotic diseases, but there can also be a risk to the home aquarist. 116dressing the zoonotic issues described above will require a "One Health" approach 119 which has been adopted successfully in combating a number of zoonoses from terrestrial animals such as zika, rabies, and hendra virus (reviewed in 120 ).A framework has already been proposed for a "One Health" approach to sustainable foodproducing aquaculture 121 and while animals destined for human consumption naturally pose a greater zoonosis risk, consideration of a similar framework for ornamental fishes is warranted.An additional complexity associated with the risk of zoonotic diseases, is the release of antibiotics and AMR genes to the environment where they can pass to human pathogens. 122Effluent from an ornamental fish market in China identified numerous antibiotics, AMR genes, and potential opportunistic human pathogens 123 and effluent from ornamental fish farms in Sri Lanka contained multidrug-resistant Aeromonas species. 124[126][127]

| Disease treatments
The prevalence and severity of diseases within ornamental fishes, along with their zoonotic potential, highlights the need for effective antimicrobial treatments."Antimicrobial" is an umbrella term which describes any chemical (synthetic or naturally derived) that kills or inhibits growth of microorganisms.As such, this spans a wide range of chemicals including disinfectants, antiseptics, antibiotics, antifungals, antivirals, antiparasitics, and antiprotozoals.In the literature, the terms "antimicrobial" and "AMR" are usually used synonymously with "antibiotic" and "antibiotic resistance," respectively.Throughout this review, where possible the class of chemical discussed (e.g., antibiotic, antifungals, disinfectants, antiseptics, etc.) will be used, accepting that some compounds may have more than one specific action.When referring to a combination of these compounds, or where it is not clearly stated in previous literature, the general term "medications" will be used.
Ornamental fish may be administered medications in different ways.Bath treatments are where the fish is added to water containing relatively low concentrations of the medication, typically for a period of 2-60 min. 128For dip treatments, fish are exposed to the chemical in a contained volume of water for shorter durations with typically higher concentrations of medications. 129Prolonged immersion can also be used, where a very low concentration of medication is introduced to the tank water for a longer exposure duration, typically many days. 128While injections are an option for treating fishes, particularly in the case of vaccination, they are usually impractical for small ornamental fishes particularly in commercial settings.This is due to their small body sizes, frequency and size of consignments, individual fish value, cost, and labour intensity involved. 130The final major route of administration is through medicated feeds.Here, fish food is coated with medications before feeding or they are added to the feed during production.This method of administration requires less medication than dip or bath treatments, but relies on the fish having an appetite, which can be non-existent in severe cases of infection. 130ere are few data on the comparative efficacy of different routes of administration, most of which come from an aquaculture setting.When silver perch (Bidyanus bidyanus) were treated with antiparasitics to control monogean gill parasites, oral treatments were comparable to bath treatments for one medication but performed worse for another. 131Some fish medications can reduce palatability leading to feed and hence medication being rejected, hampering effectiveness. 131,132In red pacu (Colossoma brachypomum) and koi carp (Cyprinus carpio koi) oral, intramuscular injections (and intraperitoneal in koi), and bath treatments of the antibiotic enrofloxacin all provided therapeutic blood concentrations. 133,134However, in the oral treatments, gastric lavages were used rather than medicated feed which eliminates the limitation of palatability but increases labour intensity significantly.In Nile tilapia (Oreochromis niloticus), the antibiotic oxytetracycline was more effective against an Aeromonas hydrophila infection when provided as medicated feed rather than as a bath treatment. 135Similarly, in common carp (C.carpio), the antibiotic florfenicol was more readily absorbed when provided as a medicated feed rather than a bath treatment. 136namental fish supply chains often involve many parties in both the exporting and importing country.Most freshwater ornamentals originate from fish farms in Asia Pacific countries such as Singapore, Indonesia, and the Philippines. 6In these farms, fishes may be treated with medications prophylactically (preventatively; in absence of disease), therapeutically (to cure active disease), and possibly in some cases for growth promotion, despite the latter having no scientific basis and some evidence it could decrease gut health. 15,137,138Obtaining data on treatments at this stage is difficult, as ornamental fish farms are typically small family operated businesses and are reluctant to share husbandry practices established through many years of trial and error. 139As fishes are traded between different parties, they could experience different medications at each stage in the supply chain, particularly during long transports between importing and exporting countries where medications are often added prophylactically to increase survival. 140,141Fishes may even be treated with chemicals banned in the destination country, as different countries have different rules and regulations on fish medication use. 125For example, in the United Kingdom, all antibiotics used to treat animals fall into class POM-V (prescription only medicine-Veterinarian) and must be prescribed by a veterinarian. 142wever, in the United States, many antibiotics used to treat fish are available to purchase online or over the counter. 143In addition, in countries where antibiotics are available, there are generally strict regulations in place for antibiotic use in finfish aquaculture destined for human consumption, but not for ornamental fish aquaculture.
Regulations do not typically exist for ornamental fishes, or are unenforced if in place. 15For example, the US Food and Drug Administration regards ornamental fishes as a low regulatory priority. 130Once the fish have reached the end user in the supply chain, the home aquarist, the choice of treatments will likely be very different to those routinely used in commercial settings, particularly in exporting countries.It is worth noting, fish are typically given quarantine periods before being added to aquaria both in a commercial setting and when kept by the more dedicated hobbyist.For example, public aquaria generally quarantine new individuals for a minimum of 30 days before introducing to established aquaria. 144During this time, typically at least 2 weeks, fish can undergo health monitoring to look for early warning signs of disease in addition to the application of a variety of prophylactic fish medications.However, while health monitoring as a preventative tool has been used successfully for tropical ornamentals within research facilities, 145,146 it is not well developed for the home aquarist.

| Treatments within commercial settings
The scarcity of data on antibiotic use within the ornamental trade was recognised by Weir et al. 15 They sought to rectify this by surveying aquaculture-allied professionals with expertise in ornamentals and antibiotic use.The surveys covered all aspects of antibiotic use in the ornamental sector including purpose, production phase, and class of antibiotic used.Most participants stated antibiotics were commonly used, mostly therapeutically rather than prophylactically.Quinolones, tetracyclines, and nitrofurans were among the most used classes of antibiotic, although occasional to frequent use was reported for all classes by at least some respondents.However, the majority of survey participants were from North America (92 out of 113; 81.4%).This becomes problematic for interpretation considering that Asia and Europe contribute $57% and $28% of global ornamental exports, respectively. 147Therefore, the surveys likely do not capture the true use of antibiotics within the trade.
Another way to obtain data on fish medication use within the trade could be the screening of carriage water for medication residues.When 50 consignments of ornamental fishes imported into the Netherlands from 13 countries were screened for medication residues, 49 of them contained one or more antibiotics at detectable levels, including antibiotics which are banned in the EU such as chloramphenicol and nitrofurans (36 and 68% of consignments, respecitvely). 125By examining carriage water samples, data can be collected on fish medication use from exporting countries independently of reporting bias.However, if medications are used early in the production cycle prior to export then there is a possibility they would not be represented.Additionally, different classes of antibiotics vary in their persistence within aquatic environments. 148Therefore, there is the potential for less stable compounds to be underrepresented.Another way to estimate use of fish medications is through sales data; however, these data are not readily available on a global scale.It is important to monitor antibiotic use within the trade as inappropriate use can result in AMR.

| AMR within ornamental fish pathogens
One of the main problems associated with the disease treatments used during the commercial phases of the ornamental trade is the emergence of AMR, a concept typically associated with antibiotic use. 149AMR develops rapidly in bacterial populations 150 and the last systematic review on the extent of AMR within the ornamental industry was published more than a decade ago. 15Therefore, an update on the subject is prudent.While recent reviews have considered AMR in aquaculture, 151 the focus is on food fishes with little emphasis given to fish kept as companion animals.Some bacteria have intrinsic resistance to different classes of antibiotics.For example, all Gramnegative bacteria possess intrinsic resistance to glycopeptides (e.g., vancomycin) and lipopeptides (e.g., daptomycin) due to reduced permeability of their outer membrane. 152Other mechanisms can confer intrinsic resistance such as the chromosomally encoded efflux pumps in Pseudomonas aeruginosa.These pumps confer resistance to a wide range of antibiotics (e.g., tetracycline, chloramphenicol, and norfloxacin) by actively transporting them out of the cell. 153This intrinsic resistance emphasises the need to establish which bacterial pathogen is being treated and target with suitable antibiotics rather than treating prophylactically.When antibiotics are used inappropriately acquired resistance can also occur.
Acquired resistance can arise through natural mutations resulting in AMR genes which confer resistance by four main routes: reducing antibiotic uptake, 154 modification of antibiotic target, 155 inactivating the antibiotic compound, 156 or its active expulsion via efflux pumps. 157AMR genes can exist in variable abundances within bacterial populations but can become more common when inappropriate antibiotic use acts as a selection pressure causing a genetic bottleneck increasing their relative abundance in the new population. 158Additionally, AMR genes are often present on plasmids, which can be transferred between bacteria through any method of horizontal gene transfer (HGT) such as transformation, transposition, and conjugation. 152,159Acquiring AMR genes is not always a benefit fitness for the organism, for example, the genes Staphylococcus aureus acquires to become resistant to methicillin and other β-lactam antibiotics also significantly decreases its growth rate. 160Regardless, the acquisition of AMR genes in pathogens makes the diseases they cause considerably harder to treat.
The rise in AMR has implications for treating ornamental fishes, and also for human health as reservoirs of AMR genes can be passed by HGT to human pathogens. 151,161This becomes particularly problematic as many antibiotics useful for treating fish diseases are also used for treating human diseases. 162To test for the extent of AMR in the ornamental trade, pathogens have been obtained from ornamental fishes by culturing swabs taken from the skills and gills, or the homogenised internal organs, or even filtered from the water.Once cultured, bacteria are exposed to antibiotics either using minimum inhibitory concentration (MIC) or disk diffusion assays to determine if the pathogens are resistant or susceptible to the tested concentrations of antibiotics. 163The prevalence of AMR within the ornamental trade is wide ranging and within most classes of antibiotic. 15Nevertheless, high resistance to penicillin, tetracycline, sulphonamide, and quinolone classes were commonly reported.
The PRISMA method was used to undertake a systematic review to update our understanding of the prevalence AMR within the ornamental industry with a focus on fish held as companion animals. 164In May 2022 and repeated in October 2023, the following search term: "Antimicrobial resistan* AND Ornamental fish*" was searched on Web of Science and Scopus retrieving articles published from 2010 onwards.The search returned 61 and 46 results from Web of Science and Scopus, respectively.After duplicates were removed 71 unique articles remained which underwent initial screening of relevance by reading the title and abstract, removing irrelevant articles (removed n = 18).The full texts of the remaining 53 articles were then assessed against the following inclusion criteria: papers presenting data from <20 isolates were not included for brevity (removed n = 11), must be original research not a review paper (removed n = 6), data must be provided on pathogens isolated from ornamental fishes or their water, data on pathogens from food fish species or a mixture of the two where pathogens from ornamentals could not be distinguished were not included (removed n = 10), article must be in English (removed n = 1), and must provide data on the percent of isolates resistant to the antibiotics (removed n = 5).An additional study was removed as it was not accessible.The remaining 19 studies were accepted, and the following data were extracted: bacterial species studied (species and number of isolates), geographical origin of samples (country and type of facility), biological origin of samples (fish species, organ sampled, water samples), antibiotics tested and percent of isolates resistant, and multiple antibiotic resistance (MAR) index (number of antibiotics an isolate is resistant to divided by the total number of antibiotics tested).Where data were only presented graphically, numerical values were obtained using GetData Graph Digitizer ver.2.26.0.20.
In the analysis of the results from this systematic approach and similarly to the findings of Weir, there was considerable variation in resistance to most of the antibiotics tested (Table 2).Generally, bacterial isolates showed relatively low resistance (mean % of isolates resistant: 2.8-22.9) to the following antibiotic classes; third generation cephalosporins (e.g., cefotaxime, ceftazidime, and ceftriaxone); carbapenems (e.g., meropenem, doripenem, imipenem); and aminoglycosides (e.g., tobramycin, amikacin, and gentamycin).High resistance was generally shown (mean % of isolates resistant: 21.2-87%) to penicillins (e.g., ampicillin, amoxicillin) and tetracyclines (e.g., tetracycline, oxytetracycline), indicating heavy use of these antibiotics within ornamental fish culture.
The results of this review are generally in accordance with Weir et al. 15 as penicillins and tetracyclines were largely ineffective in their findings.However, some classes of antibiotics performed better in recent years than in the previous findings.Weir found high resistance to cephems (the subclass of antibiotics that includes the cephalosporins and cephamycins) in some cases.In the present review, most cephems showed relatively low resistances aside from the first generation cephalosporins.As Weir does not distinguish between the generations of cephalosporins it is difficult to make direct comparisons.Conversely, some classes of drugs performed worse.While carbapenems generally showed low resistance, some studies found levels of resistance higher than those found by Weir, possibly indicating an increase in the use of these antibiotics.
Less than half of the studies reported the MAR index of the isolates they were testing (Table 2).A MAR index >0.2indicates the isolate originates from an environment with a high antibiotic presence. 179Of the studies which did report MAR (n = 7), all reported isolates with MAR >0.2.Additionally, in four of the studies, all isolates tested exceeded the 0.2 threshold.Whilst this is a relatively small sample size, it does hint at the prevalence of unsuitable antibiotic treatments within the ornamental fish trade.
In vitro assays such as MIC and disk diffusion are considered the gold standard to determine an antibiotic's effectiveness against pathogens. 180However, effectiveness shown in these tests is not guaranteed to translate to successful treatment of diseases in vivo.
Comparatively few in vivo efficacy trials have been undertaken for antibiotics used with ornamental fishes, relative to in vitro trials and there is a clear paucity in data on in vivo efficacy of many antibiotics used.Zebrafish with skin scrapes experimentally infected with A. hydrophila showed significantly higher survival when treated with the antibiotic gentamicin in ultrapure water compared to gentamicin in slightly saline water (0.9% NaCl) and the untreated infected fish. 181Clearly more in vivo treatment trials are needed on a range of fish species and pathogens to guarantee antibiotic effectiveness, allow targeted commercial treatments based on scientific evidence, and reduce the risk of AMR.It is worth noting that antibiotics are not the only class of treatment where resistance can be developed.For example, bacteria can also become resistant to disinfectants. 182Equally other taxa of pathogen can become resistant to their respective treatments such as anthelmintic resistance in monogeneans, 183 or antifungal resistance in fungal pathogens. 184However, given the scale of antibiotic use, the prevalence of bacterial disease within the ornamental fish industry, and the threat resistance poses to human health, we have focused on antibiotic resistance in this review.

| Treatments within home aquaria
The unsuitability of antibiotic treatments for home aquaria, coupled with growing concern in the rise of AMR presents the need for alternative treatments.There are a range of alternative treatments available to the home aquarist, some of which may also be used at a commercial level.Most of these treatments contain therapeutic dyes or plant-derived essential oils as their active ingredients.In a recent survey of over 350 participants, it was found that hobbyists purchase proportionally more natural products compared to retailers but also that there is a tendency by hobbyists not to adhere to manufacturer instructions for exact dosing protocols (Arapi EA, Cable J, unpublished data).In addition to this, in a home aquaria setting treatments may be administered without proper diagnosis leading to treatment failure and implications for animal welfare.To determine the quantity of T A B L E 2 Studies reporting antimicrobial resistance in bacteria isolated from ornamental fishes since 2010.Only studies containing data on n ≥ 20 isolates are reported.Antibiotics listed from least to most effective.Antibiotics with the same % resistant isolates are grouped together.MAR = Multiple antimicrobial resistance index = number of antibiotics resistant to/ total number of antibiotics tested.Where data were only represented graphically, numerical values were obtained using GetData Graph Digitizer ver. was mainly the name of the product, however, where products had generic names which generated excessive hits the brand name was specified prior to the product using the Boolean operators "." Table 3 summarises the number of articles returned and whether or not the article related to the treatment of ornamental fishes and/or their pathogens in vitro.It is immediately clear that there is a substantial lack of knowledge on the efficacy of most of these treatments even though most are marketed on a global scale.Given the lack of knowledge on specific treatments, the following sections are focused around the main active ingredients in order to highlight gaps in our knowledge and stimulate further research.

| Plant-derived essential oils
A number of plant-derived essential oils have been marketed to treat diseases within home aquaria.One such oil is cajuput oil, a mixture of essential oils derived from the cajuput tree (Melaleuca cajuputi).Cajuput oil mostly consists of terpenes, such as 1,8-cineole and limonene 186 although the exact composition of essential oils can vary seasonally and regionally and can exhibit distinct chemotypes. 187,188LAFIX (API) is a product marketed globally to control home aquarium bacterial diseases where the active ingredient is 1% cajuput oil.
The MIC and minimum bactericidal concentration (MBC) of MELAFIX on an assortment of known fish pathogens (Aeromonas salmonicida subsp.salmonicida, Listonella anguillarum, Pasteurella piscicida, Photobacterium damselae subsp.piscicida, and Streptococcus iniae) was determined using the microbroth dilution technique. 189MELAFIX was unsuccessful in inhibiting the growth of pathogens and all but one isolate had MBCs and MICs greater than the maximum concentration.
The concentration tested (up to 83.2 μl ml À1 ) was two orders of magnitude greater than the recommended daily dose of MELAFIX (i.e., dose for 7 days at 5 ml per 10 US gallon = 0.13 μl/ml).However, these in vitro tests were done in Mueller-Hinton broth, which is likely to be more nutrient rich than home aquarium water and it is possible that MELAFIX would be more successful in inhibiting bacterial growth at more representative nutrient concentrations.Additionally, testing was conducted at 37 C which would increase the volatility and hence reduce efficacy of the active components of this botanical oil.Temperature also has the potential to influence MIC testing directly. 190rthermore, in vitro MIC assays performed using emulsified cajeput oil against the pathogens A. hydrophilia, and F. columnare, significantly reduced optical density when compared to a no-treatment control (O'Brine TM, Staunton RH, Snellgrove D. unpublished data), suggesting some anti-bacterial activity.
While it is unclear the extent of the anti-bacterial activity of MELA-FIX, there is speculation that beneficial effects of the product may be due to immunostimulant rather than antimicrobial properties as there is evidence within the literature that essential oils can have antioxidant potential.In silver catfish (Rhamdia quelen) bathing in 50 μl L À1 of nano-encapsulated tea tree oil (derived from the congener Melaleuca alternifolia) for 1 h daily, reduced hepatic oxidative damage caused by experimental infection with Pseudomonas aeruginosa. 191[195] The one in vitro efficacy study mentioned above also established the effect of MELAFIX on marine and freshwater general fish health in vivo. 189 West Indian bay tree (Pimenta racemose) oil is another essential oil mixture promoted as an antimicrobial treatment for ornamental fish pathogens.PIMAFIX (API) is a product marketed globally to combat fungal infections in home aquaria where its active ingredient is 1% P. racemose essential oils.The oils consist mostly of eugenol, chavicol (phenols), and the monoterpene myrcene. 186,197No published studies were identified on the efficacy of PIMAFIX for treating fungal infections (or fungal-like oomycete infections) in fishes.However, T A B L E 3 Systematic search of common "over the counter" for treating bacterial, fungal, and parasitic diseases in ornamental fishes.The list of products was taken from "BSAVA (2020) Small Animal Formulary Part B: Exotic Pets Appendix III; Proprietary fish medicine vendors" with additional products added if identified, although will not be exhaustive on a global scale.Products were included if they were applicable to treating pet fishes destined for freshwater aquaria.Searches were performed in Web of Science (WoS) and Scopus databases in October 2022, October 2023 and June 2024.Where products had generic names which generated excessive hits the brand name was specified prior to the product using the Boolean operators air) were used to inhibit growth of two phytopathogenic fungi Phytophthora cactorum (69.1 ± 11.6% inhibition) and Cryponectria parasitica (75.2 ± 2.4% inhibition). 1980][201] However, these essential oils contain different volatile constituents to West Indian bay oil. 186,200Therefore, it is unclear if West Indian bay oil would be as effective and warrants further investigation.Regardless, PIMAFIX, in combination with MELAFIX was found to be 95% effective as an antiparasitic agent against G. turnbulli infection in guppies. 186other plant-derived treatment used within fish-keeping communities is garlic (Allium sativum).Allicin, the major active compound of garlic has broad antimicrobial capabilities with demonstrated antibacterial, antiparasitic, antifungal, and antiviral activity (reviewed in 202 ).While there are garlic-based fish keeping products on the market in the United Kingdom, most are marketed as dietary supplements or appetite stimulants, while occasionally listing disease prevention as a secondary function.Despite this, "home-made" garlic treatments are often used and can be prepared in various ways including dried, 203 crushed, 204 and minced/pureed. 203,205[206][207][208][209] Fluke infections (G.turnbulli) were controlled in guppy (P.reticulata) by using Chinese freeze dried garlic powder (0.03 mg ml À1 ), freeze dried garlic flakes (1 mg ml À1 ), and allyl disulphide (an allicin derivative, 0.5 mg ml À1 ) as successfully as a levamisole control group. 203This is in agreement with Fridman et al. 204 who found 1 h baths of 7.5 and 12.5 ml L À1 aqueous garlic extract significantly reduced G. turnbulli prevalence and severity in P. reticulata.
Additionally, when their food was supplemented with 10-20% dried garlic powder for 14 days, intensity and prevalence of G. turnbulli and Dactylogyrus sp.(another fluke) infection was significantly reduced. 204hanolic extract of garlic was found to treat goldfish (C.auratus) infected with tichonodinid ciliates (protozoan parasites) in a dosedependent manner with 15 mg L À1 completely curing the infection after 8 days of treatment. 208White spot disease in sailfin molly (Poecilia latipinna) and guppy (P.reticulata) was cured after 5 and 4 days of bath exposure to 0.1 g L À1 garlic extract, respectively. 207e effectiveness of garlic is not limited to treating parasites, when tested in vitro, crude aqueous garlic extract inhibited 80% of the growth of Aeromonas sp. and Psuedomonas sp.strains at concentrations of 0.40-0.41%and 0.99-1.43%,respectively. 205Supplementing fish diets with garlic seems to confer protective benefits.When goldfish (C.auratus) were a fed garlic paste-supplemented diet at a rate of 1 g per 100 g feed, they did not exhibit fin/tail rot up to 30 days post Pseudomonas fluorescens challenge whereas 20% of fish fed the control diet did. 205Additionally, when aqueous garlic extract was incorporated into the diet of female guppy juveniles (P.reticulata) for 80 days at levels of 0.1-0.2ml kg À1 diet, non-specific skin mucus immune parameters were elevated, with optimum levels found at 0.15 ml kg À1 . 206spite this promise, there is some concern over the effects of garlic treatments on fish health.When white spot infected guppy (P.reticulata) were given long-term (14 day) baths of a therapeutic dose of garlic extract (0.1 g L À1 ) histopathological changes were seen in key organs.A multitude of changes occurred in the gill tissue including epithelial hyperplasia, interstitial oedema resulting in severe epithelial lifting in secondary lamellae, degeneration of secondary lamellae, reduced length of primary lamellae, severe lamellar fusion, increased space between filaments, vasodilatation, and blood congestion.Whereas in the liver, nuclear pyknosis, cytoplasm, and vacuolar degeneration and hepatic necrosis were seen. 209Furthermore, fluke infected (G.turnbulli and Dactylogyrus sp.) guppies (P.reticulata) fed 10-20% garlic powder-supplemented feed showed elevated muscular dystrophy relative to untreated infected fish when histologically examined. 204Garlic treatments have been shown to cause slight fin damage in a dose-dependent manner in fluke infected guppies, although this was not quantified.However, the authors noted the damage healed relatively quickly (within weeks of the treatment ceasing). 203It is unclear whether the gill or liver tissue changes in the previously mentioned studies reverted as longer-term monitoring was not in place and hence should be investigated.
Care should be taken when dosing with garlic-based treatments.
The LC50 (the concentration which killed 50% of the treated animal) of ethanolic extract of garlic in goldfish was found to be 28.67 mg L À1 in 4 day bioassays. 208Mortality was seen from concentrations of 20 mg L À1 upwards, coupled with erratic swimming and irregular opercular movements which is close to the apparent effective dose of this extract at 15 mg L À1 .In healthy guppies, aqueous garlic extract (15 ml L À1 ) started to cause mortality after 1 h of exposure with 100% mortality shown by 6 h of exposure. 204Again, this was close to the effective dose of 12.5 ml L À1 for 1 h.The possibility of overdosing when treating with garlic perhaps limits its practicality as a treatment for the inexperienced home aquarist.

| Salt (sodium chloride)
There is evidence that salt may be an effective treatment against a range of fish parasitic diseases including Ichthyophthirius multifiliis (white spot disease).In vitro studies of short exposures (24 h) to varying levels of salt (2.5-20 g L À1 ) show the infective theronts of I. multifiliis are susceptible to salt concentrations greater than 2.5 g L À1 (50% mortality) with 5-10 g L À1 being most effective resulting in ≥95% mortality. 210Feeding stage trophonts are less susceptible and can survive 10 h of exposure to 15 g L À1 with 0% mortality, but not 10 h at 20 g L À1 . 211Salt baths of variable concentrations and lengths have been tested in vivo in a variety of food fish species such as catfish and trout with varying success.Generally, baths of 5 g L À1 or more for extended periods >7 days are effective in treating white spot in these species (reviewed in 212 ).However, there are comparatively fewer studies in ornamental fishes.
When an outbreak of white spot occurred in an aquarium retailer's stock of black mollies, Poecilia sphenops, a sea salt bath (10 g L À1 ) reduced parasite burden to zero in 3 days at 27 C without fish mortality. 213Similarly, when fingerlings of iridescent shark catfish (Pangasianodon hypophthalmus) were treated for white spot with 1% salt and elevated temperatures (24-30 C) the infection cleared up after 15 days, 214 although mortality rates were high.It is possible the infection was too advanced as salt baths are reportedly more effective in the early stages of white spot 213 ; when the same treatment was applied to angelfish, Pterophyllum scalare, and gold gourami, Trichopodus trichopterus, with a lighter parasite burden, survival was improved. 214The use of elevated temperatures was likely important as an increased temperature accelerates the I. multifilis lifecycle and hence emergence of the salt-susceptible theront stage. 60,211other parasitic disease of ornamental fishes that seems to be effectively controlled with salt is external infection with flukes.The in vitro and in vivo survival of the guppy-parasitising fluke congeners Gyrodactylus turnbulli and G. bullatarudis were tested under varying salt concentrations. 215Survival of both fluke species decreased with increasing salt concentrations, surviving <1 h at 33 g L À1 .However, when tested in vivo on guppies, Poecilia reticulata, the two parasites differed in their tolerances.To establish the preventative effects of salt, the guppies were gradually habituated to 3 or 7 g L À1 salinity over 7 days and then experimentally infected by close proximity to a donor fish while anesthetised.G. turnbulli failed to establish on 100% of guppies acclimated to 7 g L À1 whereas G. bullatarudis successfully established on $72% guppies at the same salinity.Furthermore, a similar pattern emerged when using higher concentration salt baths as a treatment for guppies already infected with Gyrodactylus.When exposed to 15 min baths (five baths for juveniles) of 15 and 25 g L À1 , survival of both parasites decreased with increasing salinity.However, G. bullatarudis was less affected by the salt baths with 73.3% efficacy at 25 g L À1 compared to 100% efficacy in G. turnbulli.These treatments should be used with caution, particularly in juveniles.Routine monitoring post-experiment showed increased mortalities in the juvenile fish exposed to the shorter salt baths.This mortality was not fully quantified and thus remains anecdotal in nature.More studies should be done to investigate the efficacy of salt baths for treating ornamental fishes with parasites.
The effectiveness of salt in treating parasitic diseases has led to speculation on its potential to treat external bacterial infections, particularly those caused by species sensitive to salt, such as Flavobacterium columnare (Columnaris disease).In vitro data suggest short baths (15 min) of 4% NaCl were 95-100% effective in killing F. columnare strains. 216However, in vivo in experimentally infected rainbow trout, Oncorhynchus mykiss, all fish succumbed to F. columnare infection by 6 days post infection despite being treated with 4% NaCl baths on days 1 (15 min bath), 3, and 5 (both 5 min baths 216 ).While the salt baths were ineffective at reducing fish mortality, a delay in mortality caused by columnaris disease was seen, potentially through salt killing bacteria shed from the fish epidermis, reducing the transmission rate to conspecifics.
Despite little evidence to suggest salt dips can be used therapeutically for bacterial diseases, prolonged exposure to salt may be effective as a preventative measure.When four species of fish, including goldfish (C.auratus) were acclimated to higher salinities for a period of 4-10 weeks, mortality was significantly reduced following experimental F. columnare infection. 217In untreated goldfish, mortality was 66.5% at 5 days post exposure to F. columnare, compared to 40.8% in fish acclimated to 1 ‰, and 0% in fish acclimated to 3 and 9 ‰.These results could be explained by reduced adherence and biofilm formation capabilities of F. columnare at salinities ≥ 3‰. 217,218Adherence and biofilm formation are both important factors in the initial colonisation of fish tissue and thus disrupting them may have been a key factor in reducing mortalities. 219ile 3-9 ‰ salinity seems to be an effective preventative measure for columnaris disease in goldfish, the long-term effects of salinity on the health of freshwater ornamental fishes are unclear.Goldfish kept for 21 days at 8-10 ‰ had significantly reduced growth, whereas koi kept at 12 ‰ for 4 months did not. 220,221Goldfish kept at 5 ‰ for 21 days showed decreased blood pH, blood ionic imbalance and alteration of gill structure with increased mucus secretion, swollen blood vessels and lesions. 222There are clear gaps in our understanding of the effects of long-term salt exposure on freshwater ornamental fish health.Additionally, salt treatments are not suitable for aquaria containing live plants as many freshwater plants are intolerant of even low levels of salt. 223

| Therapeutic dyes
There are a range of therapeutic dyes with antiparasitic, antifungal and antibacterial properties that have been used to treat ornamental fishes.Malachite green has a long history of use in fish treatment.It was first reported as a treatment for fungal infection of trout and as a disinfection treatment for their eggs in 1936. 224In the 1960s, it was demonstrated to be a useful antiparasitic agent, particularly against white spot 225 and for the rest of the 20th century was used routinely in aquaculture as an antiparasitic, antifungal and egg disinfectant.
However, in 2000, malachite green was banned in the EU for use in food fishes due to its persistence in fish tissues and evidence of toxic and carcinogenic properties. 226Despite this, malachite green is still used in many products commonly sold to control parasitic and fungal diseases in ornamental fishes.
7][228] For example, in jewel cichlid, Hemichromis bimaculatus, no harmful effects were observed at 0.25-0.5 mg L À1 malachite green for 96 h, which is greater than maximum recommended prolonged dose for ornamental fishes: 0.2 mg L À1 . 84,228However, in goldfish, Carassius auratus, and zebrafish, Danio rerio, the recommended short-bath therapeutic dose (2 ppm for 0.5 h) caused 10% cumulative mortality in both species by 14 days post treatment. 227In addition, fish treated with the therapeutic dose showed sub-lethal responses to the malachite green including reduced activity and loss of equilibrium.When the same concentration was applied over an extended period (2.5 h) the mortality was increased in goldfish (90% cumulative mortality at 14 days post treatment) but not zebrafish. 227The effectiveness of malachite green may also vary between species.When iridescent shark catfish fingerlings, P. hypophthalmus, received a combination treatment of formalin (25 ppm) and malachite green (0.1 mg L À1 ) a heavy infection of white spot was not successfully treated, 214 but the same treatment successfully resolved an infection in mollies, Poecilia sphenops, in 6 days without any mortality. 213Treatment of scaleless fishes with malachite green is not recommended due to its toxic effects 214 and is likely to be a contributing factor in the difference between these two studies.
Another therapeutic dye used in the trade is methylene blue which is used as an antiparasitic for fishes and an antifungal bath treatment for eggs.It increases hatch rate in ornamental fish eggs at 3 mg L À1 , although this is species-specific occurring in angelfish, Pterophyllum scalare, but not in zebrafish, Danio rerio. 229Methylene blue is considered to have a lower toxicity than malachite green, 230,231 but is used in higher doses to achieve the same effects (2 mg L À1 compared to 0.1 mg L À1 ) and can result in mortality in some species. 232peated exposure to 2 mg L À1 reduced growth performance and some immunological markers in goldfish. 233However, despite this, when challenged with Aeromonas hydrophilia, treated goldfish had better survival than untreated challenged goldfish.The use of methylene blue (1 ppm) in combination with 2% salt as a bath treatment was partially successful at resolving a heavy white spot infection in iridescent shark catfish, P. hypophthalmus, 214 where the salt possibly contributed negatively to treatment performance as treated fish showed extensive epithelial damage and had sloughed off epidermis. 214riflavine is another dye used for the control of parasitic infections and egg disinfection in ornamental fishes, 234 although there is little scientific evidence for its effectiveness.It is not suitable for use in ornamental fish larvae where it causes high mortalities (up to 100% in zebrafish larvae) using lower than recommended therapeutic doses. 234,235Furthermore, toxicity is increased in harder water which makes it unsuitable for treatment of fishes which thrive in harder waters such as East African lake cichlids. 235,236

| Other common active ingredients
Lice-Solve (Vet Ark) is a treatment marketed at combating ectoparasitic crustaceans where the active ingredient is emamectin benzoate.
While no studies have been performed on the product's efficacy against crustaceans, one study has looked at its potential as an antihelmintic treating the gastrointestinal nematode Pseudocapillaria tomentosa in zebrafish. 237Lice-Solve was tested at 10Â and 3Â the manufacturers recommended dose in four 24 h bath treatments.Both concentrations proved 100% effective although the weaker dose was tested on populations with less severe infections (80 vs. 30% prevalence).It is unclear if the lower dose would have been as effective with greater parasite prevalence.The safety of the product was also assessed in concentrations of 10Â and 5Â the manufacturers dose.
No mortality was seen.However, behaviours indicative of stress (rapid respiration, staying near tank bottom) were seen in the higher concentration although fish recovered on cessation of treatment.
Additionally, histological analysis of gill, liver, intestine, and kidney tissue revealed no toxicological effects.
Ethacridine lactate is a topical antiseptic, generally effective against Gram-positive bacteria and used to prevent wound infection in humans. 238However, despite being used in therapeutic products (Table 3) nothing is known about its effectiveness as treatments for bacterial infections in fishes.
Copper sulphate is an inorganic salt with various antimicrobial properties, widely considered to be an effective antiparasitic and antifungal agent.It has been used in aquaculture for many years to combat pathogens such as Piscinoodinium spp., Ichthyophthirius multifiliis, and Saprolegnia parasitica (reviewed in 239 ).Comparatively little is known about its effectiveness as an antibacterial treatment for ornamentals but there is some evidence to suggest it could be used as a preventative treatment.In channel catfish, Ictalurus punctatus, 24 h exposure to copper sulphate (25 mg L À1 ) prior to infection with Edwardsiella ictaluri reduced mortalities relative to untreated fish. 240MICs of copper sulphate for a variety of pathogenic bacteria range from 100 to 1600 μg ml À1 , 241 much higher than the 25 mg L À1 used by Griffin and Mitchell, 240 suggesting the effect was due to prior exposure rather than direct antibacterial effects.
Praziquental is an active ingredient often found in anthelmintic treatments for ornamental fishes (Table 3).A recent review has shown it has good efficacy against a number of cestode and monogenean fish pathogens in both food fish and ornamental species. 242It is relatively safe to use, with toxic concentrations rarely reached during conventional therapy.However, there is limited evidence on its environmental impacts and there is potential for resistance to develop within targeted pathogens. 242

| Euthanasia
From a welfare perspective, in severe cases of disease, euthanasia may be the most ethical solution and should be carried out humanely.
[245] However, options for the home aquarist can be limited due to the unavailability of anaesthetics to the general public in some countries.Clove oil appears to be most typically used by the home aquarist. 246][249] The ornamental fish trade is a multi-billion dollar global industry with a responsibility for the welfare of a large number of fishes that are routinely traded internationally.With mortality and morbidity from disease resulting in significant detriment to fish welfare and economic losses for the industry, our review clearly highlights some large scientific gaps in our knowledge that require urgent attention.While the types of pathogens occurring in ornamental fishes are wellestablished, within commercial practices AMR is certainly a growing problem.Building on the previous systematic review in this field by Weir et al. 15 we have shown that AMR is still an issue with many classes of antibiotics such as tetracyclines and penicillins proving ineffective treatments and some resistance being shown to previously effective antibiotics such as carbapenems.Inappropriate treatments of infections within the ornamental trade, particularly the use of antibiotics, will continue to fuel AMR with potential risks to human health.
The paucity of in vivo studies on the efficacy of antibiotics in treating ornamental fish diseases makes it very difficult to make recommendations for commercial practice.Further research into efficacy to allow targeted treatment of fishes is clearly needed.We recommend collaboration between policy makers, stakeholders within the industry (e.g., ornamental fish producers and wholesalers) and environmental scientists to develop and implement international "One Health" frameworks to curb the rise in AMR and reduce risks to human health.
Also concerning is the lack of scientific information surrounding the range of treatments available to most home aquarists to combat infections in their ornamental fishes.Our systematic review found minimal research into many of the commercial products available, and within that a predominance of in vitro rather than in vivo studies.Also lacking is consideration of the impacts of these treatments on general ornamental fish health and behaviour in order to fully evaluate the risks and benefits associated with these treatments.Many of the more traditional approaches such as salt and therapeutic dyes have significant side effects.The emergence of AMR, coupled with a consumer demand for sustainable products highlights the need to develop further treatments that can be used throughout the trade to reduce disease and improve welfare.Ideal products for disease treatment in pet fishes should have high efficacy with minimal risk of resistance developing, be non-toxic to the fish with a significant margin between the effective dose and sub-lethal effects in the fish, such as adverse behavioural responses.More research is needed to understand fully these characteristics within existing treatments, but also into the potential for new treatments to reduce disease and improve ornamental fish welfare.
Gram-negative bacteria known to cause disease issues in ornamental fishes include Flavobacterium columnare (columnaris disease), Edwardsiella spp., Aeromonas spp.(koi ulcerative disease and motile aeromonad disease), Pseudomonas spp.(pseudomoniasis), and Vibrio spp.(vibriosis).While there are other examples, these five bacteria are particularly significant for the ornamental trade; the symptoms of the diseases they cause are summarised in Table 1.There are comparatively fewer Gram-positive bacterial diseases reported within ornamental fishes; the two main Gram-positive bacteria infecting ornamental fishes held in home aquaria are Streptococcus spp.(streptococcosis) and Nocardia spp.(nocardiosis).Mycobacterium spp.
Aquaria (75 L, n = 3) were stocked with 10 clownfish (marine) or goldfish (freshwater) and underwent daily dosing with MELAFIX for 2 weeks with water changes performed on day 7 and daily for 2 weeks post treatment.No distress behaviours or histopathological changes (compared to a control tank without MELAFIX) due to MELAFIX treatment were noted.A study evaluating the antiparasitic properties of cajuput oil (at comparable concentrations to MELA-FIX) against Gyrodactylus turnbulli infection in guppies (P.reticulata) also observed no signs of behavioural distress during the first hour of treatment196 where fish were treated in isolation.While these studies suggest no negative effects of MELAFIX, behavioural observations following MELAFIX treatment have been limited to temporary distress behaviours.
Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/raq.12948by University Of West Scotland, Wiley Online Library on [25/07/2024].See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions)on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License T A B L E 3 (Continued) Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/raq.12948by University Of West Scotland, Wiley Online Library on [25/07/2024].See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions)on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License preliminary data supporting a significant reduction in fungal hyphae growth on ricefish eggs (Oryzias woworae) using PIMAFIX as a standalone treatment compared to a methylene blue control has been established (Snellgrove D, O'Brine TM. unpublished data).West Indian bay oil has antifungal properties when its fumes (28 Â 10 À3 mg ml À1