Abstract: Two wa ter purifica tion me thods wer e compared .The biofluidized bed was 3 t imes higher than biof ixed bed in ammonia N loading and ammonia N removal r ate .Distribution and gr owth of bacteria on the f luidized bio-par ticle surface was observed by electronic microscope and nut ri tive agar culture method .On the par t icle surf ace the biofilm was rich and well dist ributed .At the densit ies of 150 000 larvae/m3 , in f ifteen days , the common car p fry gr ew to 12 .58 ±0 .94mm in length and 21 .2mg in weight in the biofluidized bed system , and the survival ra te of larvae was 90 %.