Coldwater fish can have different meanings in different contexts. In the context of aquariums, it refers to fish species that do not require a heater to remain within tolerable temperatures in a typical indoor aquarium. However, most or all ornamental fish species are able to tolerate temperatures as low as or lower than room temperature, with most stenothermic tropical species having critical thermal minimums of around 10-12 °C. Although these fish are capable of surviving in unheated aquaria, their temperature preferences may vary. For example, koi, goldfish, and pond loaches are commonly considered to be cold-water fish because of their ability to survive at very low temperatures, but their temperature preferences and/or physiological optimal temperatures are 32 °C (90 °F), 24-31 °C (75