Aquarium Heaters

What Kinds of Aquarium Heaters Are There and What Is My Fish Tank Heater For?

A heater is a piece of aquarium equipment used to keep aquarium water warm - or to keep the fish tank from getting below a particular temperature.

Most aquariums have heaters, but there are often questions about these very common pieces of fish tank equipment. There are several types of aquarium heaters available, both internal (the heating element is in the fish tank) and external (the heating element is not in the fish tank). External heaters come in two varieties: in line heaters and in filter heaters, though there occasionally mention of in sump heaters (don't worry, I'll cover those too). Internal heaters come in three varieties: hanging, submersible, and substrate. All heaters also need a thermostat to switch the heater on and off as necessary to maintain the desired temperature.

Hanging Heaters

Hanging heaters are the most common and least expensive heaters available. Almost all aquarium kits contain a hanging heater to help new aquariists maintain correct water temperature. These heaters hang (as the name implies) off the back of the tank, with a glass tube containing the heater element set into the water. A hanging heater will require you to cut an opening in the aquarium hood to accommodate the head of the heater, but most aquarium hoods come with a section designed to be cut to accommodate hanging heaters or filters. It is also important to make sure you secure the heater to the back of the aquarium correctly so that it does not get knocked about, as this could break the glass sheath on the heater, posing a risk of electrocution to you and your fish, and possibly a risk of fire.

It is important to note that hanging heaters are inappropriate - even dangerous - for marine or brackish water aquariums, as the salt can get into the tube and cause corrosion or electrical shorts.

Submersible Heaters

Submersible heaters can be fully immersed in the aquarium water. Because these heaters are completely submersible, they are generally more efficient than the hanging aquarium heaters. These heaters can be placed fairly low in the water, and can be positioned vertically, horizontally, or at an angle, however, they tend to work best when positioned vertically or horizontally. If your submersible heater has an internal thermostat, it is usually more efficient if you position it horizontally in the tank, and fairly low in the water column. This will help the thermostat get an accurate reading on the tank temperature and correctly activate and deactivate the heater.

Submersible heaters are usually attached to the back of the aquarium by a clip with suction cups. It is important that you keep the heater off of the gravel, as the difference in heat conductivity between the water and the gravel could result in the glass of the heater cracking. It is also important that you provide enough space between the heater and the gravel or the side of the tank to insure that no fish will get caught against the heater and get burned.

Substrate Heaters

Substrate heaters are the least common of the internal heaters for aquarium use. Substrate heaters consist of a coil or grid of wire in an insulator which is buried in the aquarium gravel or substrate. The wire itself is the element for the heater, and when the heater is on, this wire becomes warm and heats the gravel in the tank. The heat is then radiated from the gravel to warm the water. When the water become warm enough, the thermostat will switch the heater off. Substrate heaters are supposed to be particularly beneficial for planted tanks where the gravel may act as an insulator and keep the plants' roots too cool.

In Line Heaters

In line heaters require a pump to pump the water through them, though this can usually be piggy backed with a trickle filter or UV sterilizer, and all the heater requires is water flow. The water is pumped out of the tank, through a tube or pipe, through the heater, and the heated water is returned to the tank.

In Filter Heaters

Some models of aquarium filters, usually canister filters, come with built-in heater elements. These heaters heat the water as it goes through the filter.

In Sump Heaters

Occasionally you may hear about in sump heaters. Usually an in sump heater is nothing more than a submersible heater that is set up in the sump of a trickle filter rather than in the tank itself. This configuration provides better safety for the fish by minimizing the risk of the heater getting damaged by a belligerent fish such as Oscars and by making it impossible for a fish to get caught under or behind the heater.

Other Considerations

It is important to make sure that the heater is set up so that is it unlikely that a fish will get caught between the heater and something else, such as a decoration, the side of the aquarium, or the aquarium gravel. It is also important to make sure that there are plenty of other hiding places in the tank through proper aquarium decoration so that the fish do not feel that the only hiding place is against or behind the heater. Either of these situations can easily result in severe, even life-threatening burns.

When you first set up your aquarium, or when you get a new heater, remember to always let the heater sit in the aquarium water properly set up for at least half an hour before you plug it in or begin to set the thermostat. This will give the heater time to reach temperature equilibrium and prevent the glass from breaking due to temperature differences when the heater element comes on. It is also important to make sure that the heater has been unplugged for half an hour or more before removing it from the fish tank to insure that the glass is cool and unlikely to break on contact with the air or due to water evaporating off the glass, and to prevent the heater from causing damage by burning or melting anything it may be set on.

What If I Do Not Want a Heater?

A heater is a very important part of the aquarium if you are going to have tropical fish. Many beginners forgo the heater and instead select cool water fish. There are a variety of goldfish and other temperate fish which will do quite nicely at room temperature or sometimes even cooler.

My snail mail address is: Keith Seyffarth, 217 W. Koch, #308, Bozeman, MT 59715.
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Page most recently modified: July 30 2006 20:36:18.