Recently, extensive kelp forest are decreasing at sea coastal area in Japan. The purpose of this study is to develop the technology for recovering biodiversity by multiplication of seaweed. The nutriment is mixed into the porous concrete in order to restore kelp forest in the sea area made into the oligotrophication. The nutritive substance is coated with special polymer so that the nutriment may gradually dissolve out. This paper discusses the physical properties of the porous concrete and attachment of algae to it. By considering the nearby ecosystem, the nutrient elution amount is decided. There is the technology which estimates the concentration of the chlorophyll of sea surface from the observation satellite. As a result, porous concrete with grain fertilizer coated by special polymer is thought to be useful in the recreation of well-balanced biodiversity at the sea coastal area. This technology can be also utilized for the recovery of the biodiversity in South-East Asia.