Echinoids consume and thrive on prepared feeds of appropriate consistencies, sizes, and shapes. Essential measures of the ability of echinoids to utilize feeds are absorption efficiency and assimilation in tissue production. Absorption of nutrients from various feeds prepared from soy, wheat, corn, shrimp, and fish meals, either embedded in agar or prepared as pressed pellets, are generally high. Feeds high in protein promote higher absorption of protein, but high carbohydrate content does not promote high carbohydrate absorption.
Absorption is affected by reproductive condition and by ambient temperature.
Small Strongylocentrotus droebachiensis grow more quickly on protein rich than on carbohydrate rich feeds, and more quickly on feeds containing kelp than on feeds which do not contain kelp. However, small Parcentrotus lividus do not differ in rates of growth on feeds using fish or soybean as a protein source. Large echinoids do not increase significantly in horizontal diameter or mass on prepared feeds tested. Composition of gut tissues, the immediate storage site for assimilated nutrients, is affected by both qualitative differences in feeds and the reproductive condition of the echinoid. Feeds promote maximal gonad production, even in small individuals and outside of the reproductive season, suggesting over-nourishment.