In the partial-harvest method, a number of separate large tanks for the mass culture of Chlorella and rotifers are needed, e.g., two 200-t Chlorella culture tanks along with several 40-t rotifer culture tanks. Initially, the rotifer culture tank is inoculated with Chlorella and brought to a density of 1 to 2 x 10⁷ cells per milliliter. The rotifers are then inoculated at a density of 10 to 20 individuals per milliliter. The same procedure as that described for the changing-tank method is then followed except for the use of larger culture tanks. As soon as the rotifer density is beyond 100 individuals per milliliter, one fifth to one third of the culture is harvested, depending on the reproduction rate of the rotifers. An equal quantity of the Chlorella culture (1 to 2 x 10⁷ cells per milliliter) is then added. Thus, by harvesting part of the culture and then introducing an equal quantity of cultured Chlorella, large numbers of rotifers can be harvested daily. However, due to changing water quality, the rotifer culture tank can only be maintained at peak productivity for 15 to 30 d. It must then be completely harvested and the tank cleaned, after which the same procedure as reported above is repeated. The fact that mass cultures of Chlorella may at times be contaminated with rotifers, and then fail, is a serious problem in the mass culture of rotifers (I-Chiu et al., 1993).

Rotifers can alternatively be cultured solely by being fed on bread yeast. A 3 ton concrete tank containing 2 ton of seawater is sprayed with 200 g of bread yeast suspension and the rotifers are inoculated at a level of 10 to 20 individuals per milliliter in the culture tank. The bread yeast, dissolved in fresh water, is added twice daily at a ratio of 1 g of yeast to 10⁶ rotifers. After 7 to 10 d, the rotifer density usually exceeds 100 individuals per milliliter. At this stage, they can be completely or partially harvested as feed for larvae (I-Chiu et al., 1993).