To obtain an implanting tool for a denitrifying bacterium, etc., capable of removing a nitrate salt exerting an evil influence on culturing fishes by housing a biodegradable polymer in a tube made from a synthetic resin membrane and provided with plural small holes, melt-cutting the tube for adhering the tube ends closely.

This bacteria implanting tool for a denitrifying bacterium, etc., formed by packing a biodegradable polymer material 1 with a synthetic resin membrane 3 provided with ≥2 holes 2 or by coating the same, capable of removing a nitrate salt having a low toxicity to fishes but exerting an evil influence on culturing fishes on accumulation thereof or preventing the accumulation of the nitrate salt, improving the living environment of the fishes, simplifying the culturing work for a long period of culturing fishes by a culturing worker and reducing a cost therefor, is obtained by housing the biodegradable polymer 1 in a tube 4 made from the synthetic resin membrane 3 and provided with ≥2 small holes 2, and melt-cutting the tube for adhering the tube ends closely.