When serving up fish, cook it first to kill off parasites. When offering snails, buy those that are consumable by humans so you know they are safe. Hissing cockroaches are a favorite, they love to chase them, LOL Crawfish needs to be frozen for at least 3 weeks, then thawed in a bowl of water in the microwave till warm, allow to cool, remove claws and outer thorax shell.
Good luck with your lil Nile Monster