Aquarium heaters are necessary equipment when we keep tropical fish and are used to replicate the sunís warmth. Most tropical fish live between the temperatures of 75∞F and 80∞F. Heaters warm the water safely so that the fish can live in comfort and not expend extra energy to maintain body temperature. Heaters generally consist of a glass tube housing, a heating element, and a controlling circuitry packaged inside. Heaters are divided into two main types: non-submersible, and submersible.
Non-submersible heaters clamp to the rim of the aquarium with the heating element in the water inside the aquarium. They are controlled by a bimetallic strip that bends depending on the temperature. If bent far enough, the strip touches a contact, which completes the circuit to turn the heater on. These heaters are adjusted by a knob on the top of the unit that sets the starting position of the bimetallic strip.
Submersible heaters operate in a similar fashion, but generally have more reliability and features. These heaters can be completely submerged in the water, because they are well sealed to prevent water from entering. In salt water, submersible heaters are the only choice due to the corrosive nature of the salt. Non-submersible heaters would fail quickly under these conditions. Some of these heaters have solid state circuitry which ensures better reliability and accuracy for temperature and some employ titanium alloy construction for the tube, virtually eliminating breakage problems.
When determining heating options for an aquarium, the rule of thumb to follow is 5 watts per gallon of water. Therefore, a 20 gallon tank would require a 100 watt heater. As the tank gets larger (i.e. in excess of 100 gallons), this ratio can be reduced (3-5 watts per gallon), and is a better idea to utilize more than one heater instead of one large one, as this will ensure even temperatures across the aquarium.
Temperatures in excess of 84 degrees can be harmful to the aquarium animals just as temperatures that are too cold. In cases where aquarium water temperatures are getting too warm, a chiller should be used to cool the water. Similar to refrigeration equipment, the unit moves aquarium water through coils where heat is drawn out and then the cooler water is returned to the aquarium.
The most important lesson to be learned in all of this, about water temperature, is that wide fluctuations of temperatures, high or low, are extremely stressful to the animals. In response to these fluctuations, animals must expend energy to account for these temperature changes, thus taking away the energy that was being used to maintain the animalís immune response or fight against health concerns. Keeping animals stress free by maintaining proper temperatures will go a long way in providing a healthy environment.