Rotifera Philodina erythrophthalma is well known as the valuable microorganism in a biological wastewater treatment process. The aim of this study is to make clear the method of mass culture of P. erythrophthalma for sedentary appearance in mixed culture bio-reactors by inoculation. The flask scale experiments gave the following results.1) The variety and quantity of bacterial strain as prey were not important for mass culture of P. erythrophthalma.2) The effects of accumulated metabolic products caused by microorganisms' respiration was important facter for growth of P. erythrophthalma on continuous mass culture.3) Growth factor like substances contained in rice and potato were extremely effective to mass culture of P. erythrophthalma.4) Maximum number of P. erythrophthalma in cultivation was to 12,000ml-1 by using rice extract as the growth factor like substances.5) P. erythrophthalma get through continuous high density of mass culture by replacement of cultivating solution as prevention of accumulated metabolic products.6) Inoculation of P. erythrophthalma into accomplished biota was available to be sedentary.