Aquarium denizens include FISH, snails, eels, tetras, skates, and skats. FISH are typically small, cold-blooded aquatic animals that have gills and fins. Snails are mollusks that have a single shell and a muscular foot. Eels are elongated FISH with smooth, slimy skin and no scales. Tetras are small freshwater FISH that are brightly colored and have an elongated body shape. Skates and skats are cartilaginous FISH that have flattened bodies and wing-like pectoral fins. All of these creatures can be found in aquariums, providing a colorful and interesting environment for people to enjoy.