Manually Generate Heat in Your Aquarium If the Power Goes Out

Keep Your Fish Warm in Cold Weather Conditions

Aquarium with fish

John Verive/Flickr/CC BY-SA 2.0

When the power goes out and you don't have an emergency power source to run a heater to keep your aquarium warm under cold weather conditions, here's what you can do to help keep the aquarium's water temperature from dropping to hazardous degrees. Of course, the objective is to keep your tank within the optimal temperature range, but at this point keeping the temperature even close to it will be satisfactory.

Ideally, you will have prepared for a power outage, but that does not always happen for a number of reasons. That being said, there are ways to help your tank retain what heat it does have and to add heat to keep it where it should be.

Retain the Existing Heat

The first thing to do when the power goes out is to quickly take steps to retain the heat that is already in the aquarium. Heat rises, and ​newspaper has amazing insulation properties. By wrapping the outside of the tank with thick layers of newspaper, covering the top and blocking off any hood vents, you can prevent heat from rising and escaping from the aquarium. In all likelihood, you won't be running the aquarium lights, but if you have a power source to do so, DO NOT cover the light hood, as this is a potential fire hazard. If you don't have newspaper, towels or a blanket can be used.

Manually Generate Heat

Once steps have been taken to retain the existing heat in the aquarium, here's how you can begin generating it to keep the aquarium warmed up.

  • Boil water with anything you have available, such as a portable propane camping or hiking stove, a wood, charcoal or propane grill.
  • Pour the boiled water into any type of sturdy plastic container that can be tightly sealed, but more importantly will not melt due to the high temperature of the water. We tested this method using clean one-gallon bleach jugs, and these worked very well.
  • Place the hot water-filled container in the aquarium and let it float. When the container starts to cool off, refill or replace it with a newly filled one.

Hot Water Container Usage Tips

  • You can float multiple containers. Depending on the size of your aquarium, how cold the temperature is getting or how fast it is dropping, you'll have to decide how many you want to use.
  • Some water may need to be removed from the aquarium before putting the container(s) in the tank because the water level will rise to some degree.
  • Before putting the container in the aquarium, even though the chlorine in tap water should be gone after boiling, you may want to add a touch of dechlorinate as a safeguard against container water leakage.
  • Remember, heat rises, therefore much of the warm water generated by the container will be at the surface. A good way to circulate the water throughout the aquarium is to pour aquarium water over the container, which is also the way to generate oxygen manually when the power goes out.