Tank mate selection is easy. If it fits in the Frogfish's mouth and moves, it's food, with the exception of snails, starfish, urchins, and maybe hermits. Other than that the Frogfish is more likely to be the pickee as opposed to the picker of trouble. Surprisingly the hardest part of keeping them is keeping them fed. They're an ambush predator to the max, and prefer to have their food come to them, so they often don't compete well for food. Make sure the fish is accustomed eating frozen food from feeding tongs or from hand.