Note: Our heater video features the Cobal and JBJ heaters. Instead of the Cobalt, we now have the AquaEl Ultra Aquarium Heaters (AquaEl manufactured the Cobalt Heaters). Consider the H2Pro Titanium Heater (as JBJ is no longer available).

Aquarium Heater General Info
Most aquariums require a heater to maintain a consistent water temperature. Aquatic life such as fish, coral, and other invertebrates need to be kept at certain stable temperatures. Different aquarium fish and invertebrates will need different temperature requirements. Fish, corals, and other invertebrates come from many different environments all over the world. A successful aquarium must replicate the environment they are from as closely as possible.

The temperature for tropical fish should be kept close to 78F. Tropical Marine aquariums should also be kept at 78F.

Some fish that are referred to as tropical are really subtropical. Some of the more common fish that fall in the subtropical category are: White Cloud Minows, Rosey Barbs, Variatus Platy, Dragon Gobies, and some marine Blennies. These subtropical aquariums should be kept at 72F.

Discus aquariums should be kept at 82F.

Goldfish, Sunfish, Bass, and Kio are coldwater fish. Coldwater aquariums are usually kept anywhere from 55F to 68F. An aquarium heater is typically not necessary for these fish, but aquarium chillers are used instead.

If your aquarium inhabitants are not kept at the proper temperature, they could suffer, get sick, or even die. Your aquarium can give you signs that it needs a heater. The most common sign is sick fish or lethargic fish. The most common disease is Ich, which can easily break out and become visible because the aquarium temperature has become too low. If you are not sure the heater you have is keeping the correct temperature, use an aquarium thermometer to see if the heater is working correctly.

How Much Wattage Do You Need?
The basic rule of 3-5 watts per gallon is recommended for keeping your aquarium at optimal temperatures. With cold rooms you will need more watts per gallon. For example, if you house is 75F and you need to heat a 55 gallon marine aquarium, then a 200 watt heater would usually suffice. However, if the room is 68F you may need a 300 watt heater.

Which Type of Heater Do You Need?
The most basic heater is the submersible glass heater with an integrated dial ( see OASE HeatUp Heater & Marineland Precision). These heaters tend to be relatively inexpensive. They are not likely to fail, but they are not terribly accurate. The cheaper ones can break when a large fish bashes into them. This can result in electrocuted fish and the leaching of toxic metals into the aquarium water. However, the better built ones made of pyrex glass, such as the OASE HeatUp and Marineland Precision, break very, very rarely.

More durable than glass are the AquaEl Ultra Aquarium Heaters. These are plastic heaters with electronic thermostats. They are more durable and less likely to break than glass heaters. The Ultra thermostat is more precise than the glass heater thermostats and this will result in a more accurate and even temperature.

The most durable, and usually the most expensive heaters, are made of titanium. These heaters often have a remote temperature probe and controller. With this type of heater you will have maximum durability and accuracy. We recommend the H2Pro Titanium Heaters. Your H2Pro Heater can be held securely in place with the IceCap Single Magnetic Heater Mount.

For tanks less than 10 gallons try an easy to use a preset mini-heater such as the Aqueon Flat Heater.

Heater Advice
Using more than one heater is advisable because heaters can fail, and having a backup heater will keep your tank temperature from fluctuating wildly if one heater fails. Heater failure can either be one heater not turning off or one heater not turning on. Both are a problem, but usually a heater not turning off is a bigger problem, as it results in the tank overheating. If you have two 100W heaters, and one does not turn off, then the other should not turn on and your tank should not overheat. If, on the other hand, you just had one 200W heater and it didn't turn off, that could spell disaster.

Another way to ensure you do not have heater failure is to use a backup, such as an AutoAqua Smart Temp Security. You plug your heater into the AutoAqua, and it will turn your heater off if it detects the temperature is at 83 degrees or above. The Neptune Aquatics Apex Controllers also have the ability to detect and turn off a heater that has failed to turn off.

If you do not need a heater all year long then remove, clean and store the heater when it is not needed to prolong its life.

When changing the temperature of your tank, proceed slowly. Do not turn a new heater on for at least 15 minutes so the heater may reach the same temperature as the water. This is a good idea for all heaters. and especially important with glass heaters since they can crack if there is a massive temperature difference.

Sudden temperature changes will also stress fish and corals. Change the aquarium temperature over a period of days or even weeks for best results.

The dial on an aquarium heater does not change how powerfully the heater heats, it only tells the heater when to turn on and off. If your heater is on, and your tank isn’t warming to 78 when your heater is set at 78, you don’t need to turn up the heater. You need a bigger heater.

Some heaters are more precise than others. The most precise heaters use a digital temperature controller and can be calibrated. Precise heaters are good at turning on at the exact same time every time. It is common for cheap heaters to be 2-3 degrees off, and they can not be calibrated. With heaters that can't be calibrated, just measure the temperature after adding the heater and adjust the heater setting accordingly. In other words, if you set heater at 78F, it results in the aquarium being at 80F, but you want the temperature to be 78F, just set the heater to 76F.