Generally speaking, ingredients of feed are mainly protein, starch, fat, fiber and other microelements. Proteins are the most important ingredient of aquatic feed, accounting for about 25%～55% in the formula. Proteins can be divided into plant protein and animal protein, which can be used according to the practical situation, in order to get the best effect.
    Starch is the main carbohydrate in aquatic feed, which acts as swelling agent and bonder in the extruding process. It has great influence on the gelatinization, water-resistance and appearance of the final products. The content of starch amounts to at least 10% in the sinking feed, and at least 20% in the floating feed.