Algae used to feed the prawn larvae are cultured by two different methods. One is the same-tank method, also called the large-scale production method or outdoor method, while the other is called the separate-tank method, which is also referred to as the small-scale production or indoor method. In the same-tank method, the algae are cultured as food in the same water as that of larvae by using sunlight and fertilization. In addition, natural food such as copepods, polychaetes, etc. are propagated in the same tank and are available to the prawn larvae. In the separate-tank method, one algal species or a mixture of algae is cultured in a separate tank. The cultured algae are then either provided fresh or from refrigerated material to the prawn larvae. Some of the best algae used today as food for prawn larvae are the green flagellate Tetraselmis sp. and the diatoms S. costatum, Chaetoceros sp., and Thalassiosira weissflogii (Liao et al., 1993).

The separate-tank method ensures greater larval densities, requires less space and water, and offers greater reliability, while the same-tank method is simple, less labor intensive, requires no separate algal culture, and is also much less dependent on the use of Artemia, the dried cysts of which are expensive and can be difficult to obtain. The question of which of these two methods is economically superior clearly depends on local needs and limitations (Liao et al., 1993).