Provided is a nitrifying bacterium inhibitor containing, as an active ingredient, a substance which is approved as a food additive, is highly safe and is slightly corrosive to metallic materials. A nitrifying bacterium inhibitor containing thiabendazole as an active ingredient. It is preferred that thiabendazole is added in the form of a slurry that is prepared using a thickening agent comprising a food additive material such as sodium polyacrylate. A method for inhibiting a nitrifying bacterium, which comprises adding the nitrifying bacterium inhibitor to an aqueous system of interest in such a manner that the concentration of thiabendazole in the aqueous system becomes 3 mg/L or more.提供一種硝化細菌抑制劑,其係將被核準作為食品添加物、安全性高,且對於金屬材質之腐蝕性為低的物質作為有效成分。一種含有噻苯咪唑(tiabendazole)作為有效成分的硝化細菌抑制劑。噻苯咪唑較佳經由聚丙烯酸鈉等之食品添加物素材所成的增黏劑,以漿料狀來做添加。一種硝化細菌抑制方法,其係將該硝化細菌抑制劑以噻苯咪唑濃度成為3mg/L以上之方式添加至對象水系中。
