PROBLEM TO BE SOLVED: To provide an alga adhesion base for sweetfish, surely adhering and growing algae which become good-quality bait essential to grow sweetfish, in a condition that the Japanese river has a fast current.SOLUTION: This alga adhesion base is obtained by adding a plant activator and a fixation agent to an aggregate, and a porous regional metamorphic rock including as the main ingredients, SiO:63.9-78.3% (wt.%, the same hereinafter), AlO:11.6-14.2%, FeO:3.60-4.40%, MgO:1.52-1.86%, CaO: 1.73-2.13%, KO:2.70-3.32%, and PO:0.054-0.068%, and other trace elements in the remaining part, mixing the product to homogenize, and solidifying the mixture in an arbitrary form. The base is fixedly laid in a river to adhere and grow algae on the alga adhesion base, and use the algae for bait of sweetfish.
