The study on the feeding intensity and its relationships with food concentration, food quality and cultural duration of Guangzhou and Wuhu Brachionus calyciflorus strains showed that the filtration and ingestion rates of the rotifers decreased with their increasing cultural duration. Within 20 hours, there was a curvilinear relationship between the filtration rate of both the two strains and food concentration, but a linear relationship between the ingestion rate and food concentration. The filtration rate of Guangzhou and Wuhu strains was 0.0029 +/- 0.0001 ml x ind. (-1) x h(-1) and 0.0039 +/- 0.0008 ml ind. (-1) x h(-1), respectively, when fed on Chlorella pyrenoidosa, which were higher than fed on the other two types of food. The ingestion rate of Guangzhou strain fed on Chlorella pyrenoidosa (0.3992 x 10(4) +/- 0.00850 x 10(4) cell ind. (-1) x h(-1)) was higher than that fed on Scenedesmus obliquus (0.1670 x 10(4) +/- 0.0370 x 10(4) cell x ind.(-1) x h(-1)), but each of them was similar with that on mixed algae. The ingestion rate of Wuhu strain was not significantly affected by food type. The filtration and ingestion rates between the two strains differed with food concentration, food type and culture duration.