These fish prefer cooler water temperatures than tropical fish. They typically prefer temperatures below 20 °C (68 °F) and therefore are also know as Pond Fish. They are perfect for outdoor ponds. Some of the best known examples are Koi and Goldfish.
These species tend to grow more slowly and live longer than fish that live in warmer waters, and are generally felt to be easier to keep. The smaller varieties of the goldfish known as Fancy Goldfish are extremely popular and are very often kept in indoor Aquaria.