Tetras are small, freshwater fish popular in aquariums. They come in a variety of colors and are known for their peaceful nature. However, the word "tetras" can also be replaced with synonyms such as Characins, Rasboras, or Danios, which are all types of fish that share similar characteristics with tetras. Characins are also peaceful fish and are great for community aquariums. Rasboras are known for their active behavior, and Danios are a hardy species that can adapt to various water parameters. Whatever name you use, these fish are colorful, fun to watch, and great additions to any aquarium.