Gammarus pulex are small (2-3 cm) crustaceans of the order Amphipoda. They are an important dietary component of fish in the wild. Dried and easily applicable Gammarus pulex are the source of macronutrients, trace elements and beta-carotene – natural carotenoid. Beta-carotene intensifies fish's coloration, facilitates many physiological processes, keeping fish in excellent condition. But above all, Gammarus pulex are the source of chitin – rougha