The effects of four diets [yeast-Cerophyl-trout chow (YCT) and YCT plus three concentrations of supplemental Selenastrum capricomutum] on the vitality and fecundity of five life-span generations of Ceriodaphnia dubia were determined. There was no significant difference among the diets for the five generations. Trends, however, indicated an increase of young production, especially during the first seven days, for successive generations. A subsequent seven generation, seven-day test was conducted to confirm young production trends observed in the life-span test for the YCT diet and the YCT plus 10^7 cells/ml algae diet. Although intensive individual culturing could account for much of the improvement in young production, the algae supplemented diet of 10^7 cells/ml had significantly greater young production than the YCT diet.