Fish

Fish were swimming in Earth’s waters long before the first animals crawled onto land, and they breathe by pulling oxygen from water through their gills. Many of the most popular aquarium species come from warm tropical rivers, where bright colors help them recognize mates and warn off rivals.

This section focuses on fish people keep, from beginner favorites like the guppy and the betta fish to schooling species such as the neon tetra and outdoor pond giants like koi. Profiles cover natural habitat, diet, tank or pond setup, temperament and breeding, so families and new fishkeepers can choose companions that suit their space.