Water Quality: Temperature
Temperature plays a vital role in the survival, growth and reproduction of fish. Each species of fish has its own temperature range for survival and, within this range, a narrower range at which the fish will reproduce and exhibit optimal growth. Fish are cold-blooded, so their metabolism is directly affected by water temperature. As temperature increases, a fish's need for oxygen and food increase. In addition, the immune and enzyme systems of fish work best at their preferred temperature range.
Most fish in the aquarium trade, with the exception of koi and goldfish, are considered warm water or tropical species. An aquarium heater may be required to maintain adequate water temperatures. Every effort should be made to ensure that fish are not exposed to broad or rapid changes in water temperature. These changes are stressful to the fish and can result in death. New fish being added to an aquarium should be slowly acclimated to the temperature of their new environment before stocking. Once stocked, the water temperature of an aquarium should be checked every day to ensure that it is stable and within the optimal range for the tank inhabitants. Fish with extremely different temperature requirements should not be housed together.