Ok, seriously that’s a tough one. I’m going to assume African Dwarf Frogs aren’t unique enough. There might be some small salamanders that could work, but I can’t think of anything specific (not talking about axolotls). The best I can come up with are Leopard Crabs and Dwarf Mexican Crayfish. Leopard crabs are pretty cool in that they’re fully aquatic freshwater crabs, but aren’t super tiny like the Pom Poms.