Black worms are a naturally occuring aquatic worm that is commercially cultivated and then dried in a way which retains all their goodness. Black worms are an excellent, natural, high protein food for tropical fish and turtles. It is an excellent food for finiky eaters and also for conditioning fish for breeding. Feeding: you may feed your fish several times a day, but only as much as they can eat in 5 minutes. Nutrition facts (Dry Weight Basis): crude protein: 66. 35% crude fat: 13. 87% crude fiber: 0. 24% moisture: 3%.