Crayfish are aggressive omnivores. They are opportunistic little guys. If they see a chance to snag something and eat it, they will. That means, yes, crayfish will eat the fish in your tank if given the opportunity.

Can crayfish live with fish?

Crayfish do best when given the run of a spacious tank. However, they'll generally live in relative harmony with small fish like goldfish, barbs, mollies, swordtails, and neon tetras. Crayfish may display some aggressive tendencies from time to time, but they're usually too slow to catch and eat the much-faster fish.

Will crayfish eat fish in aquarium?

Crayfish will typically eat whatever they can catch, but since they are slow-moving, they are rarely able to harm most types of fish or shrimp. They prefer foods like invertebrate pellets or blanched vegetables (such as zucchini, carrots, and spinach), but will also eat fish food and algae wafers.