The crayfish, or crawfish, is a freshwater invertebrate. It looks like a small lobster. Like other invertebrates, it grows by molting -- a crayfish sheds its shell when the animal outgrows it and then grows a new one. Most species grow up to 6 inches, but some can grow longer. They can be kept in small aquariums. Duplicating its natural diet will keep it healthy. Crayfish are omnivorous scavengers, but mostly feed on algae, plants and detritus.
Offer a variety of vegetables. You can feed your crayfish frozen peas, lettuce and other leafy greens, and boiled carrots and zucchini. Experiment with different vegetables -- perhaps your crayfish is partial to one over another.
Feed your crayfish staple plant-based aquarium foods, such as sinking algae pellets, flake food and dried seaweed. All of these can be found in any local fish store.
Give your crayfish an occasional protein-based freeze-dried or frozen food, such as bloodworms, brine shrimp, krill and tubifex worms, also found in local fish stores. Please note that that these foods are only supplemental; the majority of your crayfish's diet should be plant-based foods.