Freshwater clams, cherry shrimp, ghost shrimp, brine/fairy shrimp, hydras, apple snails, rashorn snails, african clawed frogs, 'tutti fruity' frogs, blood worms, tubefex worms, black worms, newts, 'water dogs', tadpols, some species of water bettles, fiddler crabs (they need to be able to get out of the water sometimes though), water scorpions (if they're with compatible fish, crawfish, and others.