The term 'NEON TANK FISH' refers to a type of aquarium fish known as Neon Tetras (6 letters). Neon Tetras are small, freshwater fish native to South America. They are popular in home aquariums due to their bright colors and peaceful nature. Neon Tetras have a silver body with a bright red-orange stripe running along the length of their body. They are also known for their ability to school together in large groups.