While thousands of zooplankton species could potentially serve as food for larval stages of cultured fish and crustaceans, the aquaculturists practical choice of a reproducible live food ratio is quite limited. In practice, rotifers and brine shrimp are the most commonly used zooplankton for these critical larval stages. The reasons for the popularity of these organisms lies in the fact that they are easily obtained or cultured, are of appropriate size, and have been shown to support a wide spectrum of larval forms. Recently, aquaculturists have turned their attention to the quality of the rotifers and brine shrimp that are being fed. The brine shrimp has been shown to have a limited capacity to biosynthesize long-chain fatty acids and, thus, its nutrition takes on added significance. An Artemia reference sample is now available, so that one can compare the growth and survival of experimental animals fed the reference brine shrimp versus those fed an acquired batch of Artemia.