Supplemental feeding compensates for natural food nutrient deficiencies in fertilized ponds and is the usual feeding method for semi-intensive tilapia culture systems. A comprehensive review supplemental feeding practices and of various supplementary feeds is provided by Tacon (1988) and De Silva (1995). The use of supplemental feeds leads to significant increases in tilapia yield in comparison to fertilized ponds alone. However, farmers must be aware of the complex interactions between the natural food supply and supplemental feeds and that incorrect feeding strategies can lead to financial loss. Supplemental feeding should be carried out properly coupled with a good understanding of the nutrient content of the various feed ingredients (Table 8). Supplementary feeds can be made up of single ingredients or combinations of ingredients either simply mixed together or powdered and compounded into moist dough before feeding. The most common feedstuffs are agricultural by-products such as rice bran, broken rice and maize with occasional use of grass and leaves. Dry ingredients are normally ground before being dispersed throughout the pond. However, many raw ingredients of plant origin are inappropriate for tilapia fry, but can be used for fingerling and larger fish. It should be mentioned that commercially formulated pellets can also be considered as supplementary feed when used in combination with a pond fertilization regime, or used in combination with cheap feed ingredients. Some farmers often use formulated feed as a single feed source for a particular life stage.
