With wintertime comes colder temperatures, both inside and outside.

It’s around this time each year I begin to see threads popping up on forums discussing aquarium heater failure. Sometimes they are lucky: the heater simply did not turn on and their tank got colder. In other instances, heaters overheat or crack and the results are disastrous. I actually experienced heater failure myself this season. Fortunately, my heater only stopped working so the tank temperature dropped a bit.

Dealing with heater failure is an inevitable part of caring for a temperature-sensitive aquarium system. If we keep that in mind—that aquarium heaters can and will, eventually, fail—we can prepare accordingly to protect our precious pets from temperature fluctuations.

Here are some tips to help you safeguard your aquarium from heater failure:

  • Research the various aquarium heaters available for your tank. Nearly all the heaters on MarineDepot.com have customer written reviews about their performance. This feedback is invaluable when making a purchasing decision. Starting with a high quality heater minimizes the chance of failure.
  • Use a temperature controller (or system controller) to turn the heater on and off. While most heaters have built-in thermostats to turn the heaters on and off, many times this is precisely what causes the heaters to fail. The thermostats “stick” in the on or off position and the heater will not properly energize or de-energize. A temperature controller will turn on/off the heater independent of the thermostat built into the heater.
  • When using a temperature controller in combination with a heater, set the temperature on the controller a degree or two cooler than the thermostat on the heater. This way in case the controller fails to shut the heater off, the heaters thermostat will shut it off.
  • Consider using multiple heaters instead of a single heater. If your tank requires around 500 watts of heating power (it is recommended to use 3-5 watts per gallon), try using two 250 watt or three 200 watt heaters. This will help in a couple of ways. First, if one heater fails, you have a back-up heating the tank. Second, if a heater gets stuck in the on position, it will raise the temperature more slowly than a single larger wattage heater (hopefully allowing you to catch it before an issue arises).
  • Heater placement is also very important. Knowing that heaters can fail, don’t hide the heater underneath a pile of rocks that could make it difficult to excavate in the event of failure or make it impossible to visually inspect it. As well you will want to provide good water movement around the heater to allow for the heated water to circulate throughout the tank. If you have a sump on your tank this can be an ideal location for the heater.
  • Protect glass heaters from falling rocks or other objects/livestock that might cause it to break. Titanium heaters can get hot enough to melt acrylic, so never put a heater directly against an acrylic tank or sump.
  • Don’t trust with 100% accuracy the dial on the heaters thermostats. It is common for heaters to heat accurately, but for the temperatures to not match the numbers on the dial. Trust the reference thermometer(s) and set to them, not the dial.
  • Use more than one thermometer to measure the temperature of your aquarium. Don’t rely on a single reading. Thermometers come in a range of styles and prices. There are even some models that will alert you when the temperature rises too high like the Lifegard Aquatics Big Digital Temperature Alert or Tom Aquatics Aquarium Temp Alert.

  • If you already own a chiller or are considering purchasing one for the warmer months, you may want to find one that has a dual stage controller that allows you to control both your heater and chiller (this can prevent them from both being on at the same time as well).
  • Have a back up heater ready to go, especially if you are only running a single heater on your system. It is a small investment to help protect your livestock.