Bright aquarium fish are a popular choice for home aquariums due to their vibrant colors and interesting behavior. Two of the most popular bright aquarium fish are the Tetra and the Betta, both of which have five letters in their name. The Tetra is a small, schooling fish that comes in a variety of colors and is known for its peaceful nature. The Betta is a larger, more aggressive fish that is also known for its bright colors and long fins. Another bright aquarium fish is the OPAH, which has four letters in its name. The OPAH is a large, predatory fish that is known for its unique coloration and its ability to change color depending on its environment.