Do Fish Tank Heaters Turn Off Automatically?

Do Fish Tank Heaters Turn Off Automatically?

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An aquarium’s ability to stay warm is one of most important components because it determines the well-being and comfort of aquatic life. Since fish don’t produce their own body heat, they have to have their environment maintain a steady temperature. So, if you’re new to the hobby, you may wonder, “Do fish tank heaters turn off automatically?”

Yes, there is an automatic mechanism that shuts down fish tank heaters. Manufacturers design them to turn off when they reach the preset temperature. When the temperature drops below that setting, it turns back on.

Will a fish tank heater turn off automatically?

Since all fish tank heaters have an automatic off or on mechanism, there’s no need to worry about overheating. All you have to do is set the appropriate temperature and the heater will take care of the rest.

Can a fish tank heater burn fish?

If you have concerns about the heater burning your fish, in most cases, the tank shouldn’t stay on if it’s malfunctioning. Many manufacturers engineer heaters with a safety shutoff. This means you don’t have to to worry about damage to fish.

The only time a heater can hurt fish is if you set the temperature too high or it’s summertime. Even if a heater turns off because the temperature is warm enough, sunlight exposure, humidity and general termperature can cause damage to fish.

What are the types of fish tank heaters and how do they work?

There are generally two types of tank heaters: mechanical and electronic. Both work in a similar fashion with a few differences.

Mechanical heaters (see Amazon) have two dissimilar metals bonded together on a strip. These expand and contract at a different rate when cooled or heated which causes the strip to curve as the temperatures change. You can adjust this bimetal strip to increase or decrease in temperature by way of a coil or spring attached to a dial.

Electric heaters have a sensor that picks up temperature increases and decreases. It adjusts the voltage output as necessary and it turns itself on or off automatically.

How will you know when a tank heater isn’t working?

Tank heaters often have an indicator light showing when it’s on or off. But, it’s best to use a thermometer in your tank so you can monitor the temperature daily. If you notice the light has not come on and there’s a noticeable temperature drop, chances are, the tank heater isn’t working.

How do you keep fish warm without a heater in an emergency?

In the event the tank heater stops working because it’s broken or there’s a power outage, there’s a couple things you can do. Use the following tips and methods when you experience an emergency situation:

  • Check Fail-Safe Measures: If you have pre-installed backflow tubing and sump shutoffs in place, ensure these are on and active.
  • Insulate the Filtration: Do whatever you must to keep your filtration system warm; wrap it up with towels, blankets  or cardboard.
  • Insulate the Tank: Cover all sides of the aquarium, even the top and sides, to prevent heat from escaping the tank. You can use cardboard, sheets, blankets or some other kind of barrier.
  • Ensure Oxygenation: Even though you want to maintain heat within the tank, you have to allow ample room for the tank’s oxygen supply. The fish and plants have to breathe.
  • Leave the Fish Alone: Avoid checking on your fish once you insulate everything and ensure oxygenation. This is because every time you remove the temporary insulation layers, you release essential heat.
  • Temp Drops Beyond Insulation: If the temperature begins dropping to dangerous levels, fill a sealed bottle with hot water and put it into the tank. For instance, if you’re going for 80°F, then make sure the water within the bottle is 120°F.


Although fish tank heaters turn off automatically, you will have to keep an eye on it if you suspect it’s starting to fail. Look at the thermometer and make sure the indicator light turns on and off at the appropriate times. The moment you notice it isn’t working, you will have to take immediate steps to protect your tank.

See Also:
Why Are Fish Tanks So Expensive? (Detailed Explanation)
Can You Use Spring Water in a Fish Tank?
Can You Clean a Fish Tank with Soap?
Is Cloudy Water Bad for Fish?