Two diets were compared for the cladoceran, Ceriodaphnia reticulata, for use in culturing and life-cycle toxicity tests. One diet was a suspension of dry yeast dissolved in distilled water and fed at a rate of 250 µg per animal. The other diet was prepared from frozen adult brine shrimp (Artemia salina) and distilled water, the aged supernatant of which was fed using 0.05 mL per animal. Animals were fed daily and water changed three times each week. The feeding study was conducted for ten generations using young per female and adult survival as endpoints. The young production per female of surviving adults was comparable, but the longevity of the animals fed the yeast diet was considerably greater than that of the animals fed the shrimp diet.