All of our efforts as a hobbyist are specifically curated to create a safe environment for the corals and fish in our aquariums. Even the slightest change in temperature, chemistry, lighting, flow, or water quality can mean disaster for your aquarium ecosystem. Knowing how to properly control those environmental conditions, identify problems, and prepare for the inevitable can be the difference between success and failure. 

Needless to say, having quality equipment that you can count on will go a long way in preventing problems but harboring the false hope that your equipment will NEVER fail just isn't a reality. Every single piece of equipment on your tank can and eventually will fail. The key to avoiding disasters is keeping a close eye on your aquarium with redundant monitoring solutions and being prepared for the inevitable failure. 


Aquarium heaters failure is the #1 most common aquarium device that leads to some kind of disaster. A majority of those disasters revolve around changing water temperatures. Whether it gets too hot or too cold, the drastic change in temperature can be detrimental.  


Identifying problems with water temperature is pretty straightforward, pay absolute attention to water temperature at all times.

  • Use multiple thermometers and set up alerts for changing water temperatures.
  • If you notice livestock is suffering, the water temperature is one of the first parameters you should check.
  • If air temperature around the aquarium plummets or gets uncomfortably hot, it will affect your tank's water temperature.
  • Simply sticking your finger in the tank water is enough to identify when temperatures have fallen out of range. 
  • Water temperature in your display aquarium is what matters most and the temperature in your sump may be different. Monitor both. 


Don't rely on a single thermometer. In addition to your heater's temperature controller or built-in thermostat, use a separate thermometer that can give you a real-time indication of water temperature at a glance.

Set up some kind of alert that will notify you when temperatures fall out of range. This can be accomplished in a number of ways and having multiple alerts is always a plus. Audible alarms would simply make a sound when temperatures fall out of range, visual alarms would be something like a red flashing light, and remote alerts would be getting an email or push notification on your cell phone. The rise of "smart" devices is making this easier to accomplish around your aquarium. 

Ultimately, as long as you are notified right away you can act immediately to correct the problem before it is life-threatening. In the event that you experience a temperature problem, be prepared to handle it.  

  • Keep backup heaters on hand at all times and/or replace heaters annually to prevent failures. Especially important in cold climates. 
  • Use an aquarium controller as redundant protection to turn off your heaters in the event of rising temperatures.
  • If you live in a warm climate, keep an aquarium fan on hand and consider owning a chiller. You don't have to use your chiller all the time, just keep it on hand. 
  • If you live somewhere with a cold climate, use the dual heater approach. Have a second heater programmed at 2-3 degrees lower than your primary heater, should temperatures start to fall the second heater will kick on and help maintain water temperatures.