Commercial single-cell proteins either as sole food source or in formulated diets for intensive and continuous production of rotifers (Brachionus plicatilis)

Commercial Spirulina, Chlorella, and a methanol-grown yeast were tested as sole food source for the rotifer Brachionus plicatilis. Some good results were obtained, but only with medium salinity (18%) and none with seawater (35‰). In comparison with a constant supply of food, different adjustments of the food level to the population density were tested: a proportional and continuous or stepwise adjustment and a less proportional one. The less than proportional adjustment was found to be more advisable for a continuous culture with a daily renewal of a quarter of the volume. The three single-cell proteins appeared to be suitable with 35–55 rotifers produced per ml per day. However, the food conversion was poor: in the best cases 4.2 g of food were required per 10⁶ rotifers produced. In practice, two formulated diets were preferred for mass culture trials in 60-l tanks: the first (P 72) included 40% Spirulina, 40% yeast and different additives; the second was composed of 67% of diet P72 and 33% of the freeze-dried alga Platymonas suecica. The production was 44 and 35 rotifers, respectively per ml per day, with 3.6 and 2.9 g of food, respectively per 10⁶ rotifers,produced. Freeze-dried algae did not appear to be necesary for rotifer production, but the nutritional quality of such rotifers should be investigated.