Question: how big are tetra fish?
Answer: They can have a lifespan of up to ten years, or normally about five in an aquarium. Neon tetras reach 3.5 cm in length, and are considered easy to keep in a community aquarium of at least 50 cm (20 in) long, with a pH of 6.0 to 6.5 and a KH of 1.0 to 2.0.