Learn About Aquarium Heaters


Many people do not realize the importance of the stability of the right temperature in aquariums.

In the wild, fish live in millions - no, billions - of gallons of water. The temperature of vast rivers, lakes, or oceans is not affected by daily or hourly swings in the temperature of the air around them. There is simply too much water to alter the temperature up or down quickly. Change happens slowly over weeks or even months.

Aquarium water, on the other hand, is in relatively small quantities. The daily fluxuations in the ambient temperature of your house has a very direct affect on the temperature of the aquarium water.

Fish cannot regulate their own body temperature so depend on the temperature of the water to keep a stable body temperature.

Fish do not have the ability to regulate their own body temperature. The fluids inside their body are directly affected by the temperature of the water. Given frequent and fairly fast changes in their environmental temperature, their systems are figuratively "torn assunder" by temperature swings.

A fish stressed by temperature fluxuations cannot fight the ravages of normal populations of bacteria, protozoa, and parasites, thus succumbing to them.

The change in temperature between daytime and night time in the average home causes enough stress to a fish's system to begin to see a compromised immune system leading to disease, parasites, and death. (You've heard that ich is caused by temperature fluxuatons? Of course, temperature never caused parasites. However, a stressed fish cannot fight the ravages of normal populations of bacteria, protozoa, and parasites, thus succumbing to them because of "temperature fluxuations".)

Most tropical fish enjoy a temperature of about 76°F to 78°F Most corals can survive in this temperature. However it might be best to learn what the native temperature of your tank inhabitants is. Keeping reef invertebrates from different regions with wildly disparate temperature requirements is really unwise, as you can't satisfy them all in one system.

An aquarium heater does not have to be complicated for most hobby tanks

An aquarium heater has a thermostat that turns it on when the temperature of the water goes below that setting and turns it off when it reaches that temperature. An aquarium heater does not have to be a complicated instrument to prevent temperature fluxuations, and this feature alone is enough for many situations.

Submersible heaters are the most popular type and the one we will discuss in this article. They are used completely submerged in water. The main differences in submersible heaters comes in their placement, their type of controls or their size.

MOUNT: Most heaters mount vertically to the wall of your aquarium or sump using suction cups supplied by the manufacturer in the package. Some can be mounted horizontally, but not all. If this is important, know it ahead of time.

Some have covers to protect them or to camouflage them in the tank.

Some can be mounted through the top of your canister filter, heating water as it passes through the filter instead of inside the tank. This has the advantage of more consistent temperature control (as all water passes over the heater and is more evenly heated). It also keeps the possibly-unsightly heater out of the panorama of the tank interior.

Generally speaking, purchase a heater that gives approximately 4-5 watts per gallon of water to be heated.

WATTS: It is a good idea to purchase a heater that gives approximately 4-5 watts per gallon of water to be heated (assuming the aquarium is not in a very cold room where the temperature will have to be raised a great deal. In that case purchase a larger heater).

It is also a good idea to purchase two heaters for redundancy. What is redundancy? It is the use of two in case one quits working. You will have time to replace it without your tank crashing.

SETTINGS: Some knobs are easier to grasp, turn, or see the settings. Some heaters can be adjusted and finely tuned to 1°F. It's nice to have fine controls. It's also nice to have a light that tells you at a glance when it is on and when it is off. Purchase one that has temperature readings that suit your eye sight.

You will probably need a thermometer to check the water temperature to be sure the heater is doing its job.

SAFETY: Some turn themselves off if left without water - a good idea if they are likely to be left high and dry or you accidentally pull it out and lay it down without unplugging it. Many are made of shatter-resistant materials - also a good idea.

MEASUREMENTS: It's necessary to know how deep your tank is to fit the actual dimensions of the heater inside the tank, sump or filter.

SUMMATION: A heater should be considered a critical piece of equipment, as fish cannot regulate their own body temperature and get stressed by temperature fluxuations.

Heaters are not very expensive. A quality heater will keep a more steady temperature over a longer period. The more automatic they are, the better control you will have over your tank with the least effort. Your fish will be happier and healthier. There are a lot of more complicated issues that you will deal with in the aquarium hobby. Leave the easy stuff to a good heater so you can concentrate on the things that use your brain to higher purpose.

See the article on aquarium chillers if you are using lights, pumps and other electrical equipment likely to keep your tank too warm.