Small aquarium fish are a popular choice for home aquariums due to their small size and vibrant colors. Tetras (6 letters) and Tetra (5 letters) are two of the most popular types of small aquarium fish. Tetras are a group of small, freshwater fish that come in a variety of colors and sizes. They are known for their peaceful nature and ability to live in groups. Tetra is a genus of small, freshwater fish that are closely related to tetras. They are also known for their bright colors and peaceful nature.