In high density culture of rotifer, a large amount of suspended organic matter accumulates in the culture medium. Such wastes are mainly composed of rotifer feces, amictic egg shells, microbes (bacteria, protozoa, fungi etc.), the food organism Chlorella and flocks of various sizes are formed and coagulate. The increase of flocks in culture medium causes clogging of the nets in harvesting of rotier and also causes pollution of the larval rearing tank by providing pathogenic microorganisms. In order to remove the flocks, a filtration unit was developed, which was composed of nylon filtration mats and stainless steel frames to aid mixing of the culture medium. In order to investigate its efficiency, changes in the quantities of rotifer and wastes (the large amount of suspended organic matter) were determined by the centrifuge method.
The culture of rotifer was carried out in two 500l tanks by the semi-continuous method with or without filtration for five and nine days. While the flocks increased in the culture medium without filtration, the flocks larger than 30μm could be efficiently removed with filtration and culture was feasible at a rotifer density of 104 ind./ml.
