Coldwater fish, in the context of aquariums, refers to fish species that do not require a heater to remain within tolerable temperatures in a typical indoor aquarium. Some examples are koi, goldfish, weather loaches, hillstream loaches, many species of barbs, sunfish of the family Centrarchidae, many Central American cichlids, and a variety of other species. Some, but not all, of these species are capable of surviving in very low temperatures, including ponds, lakes, or rivers that freeze over winter.