Crawfish, or crayfish, eat just about anything edible in their environment. This includes much water plant life and smaller aquatic animals, such as dead fish and shrimp.
The tendency of the crawfish to eat just about anything in their surroundings makes them extremely easy to care for as pets in captivity, as they don't require much of a special diet. However, this tendency can cause more trouble for owners with existing aquatic pets and aquarium plant life, as rarer plants and other pet animals are susceptible to being eaten by a crawfish kept in captivity. For this reason, crawfish are not particularly advised in large, and otherwise populated, aquariums.