What are the Reasons for Aquarium Heater Smoking? How to Prevent It?

Smoke may result from an aquarium heater that is operating at an excessively high temperature. Defective aquarium heaters can also cause smoking. Consequently, the fish in the aquarium may pass away unexpectedly.

If you switch on the heater outside of the water, the problem can also arise. An electrical gadget emitting smoke is never a good indication.

In this essay, I’ll explain the causes of aquarium heater smoking. Continue reading to discover how to avoid this problem from occurring and how to treat the fish that are impacted by it.

Why Does the Aquarium Heater Produce Smoke?

The heaters inside the aquarium can produce smoke for several reasons. But it is not a common problem in the fishkeeping hobby. Take a look at the causes of smoke coming out of an aquarium heater:

  1. You have turned on the heater before putting it inside the aquarium water.
  2. You have forgotten to turn off the heater during the water changing process. This is the most common reason.
  3. The temperature of the heater is set to very high. This can happen due to accidentally controlling the dial.
  4. There is a sudden high power surge that has damaged the aquarium heater.
  5. The heater is very old. The chances of a heater smoking increase after using it for more than 3 years.
  6. The water inside the aquarium has gotten low and the heater is exposed to the outside air. As a result, the heater overheated due to reading the temperature of the air.
  7. The on/off switch of the heater got stuck in the “on” position.
  8. The glass heater has cracked and is producing smoke.

Most of these issues can be prevented if you stay cautious. So, keep a close eye on the heater while operating it.

How to Prevent Aquarium Heater Smoking and Use It Properly?

There are several precautions that you should always maintain to prevent any kinds of accidents. Since you are submersing an electrical device inside water, you should always be careful.

Follow these tips to prevent your aquarium heater from malfunctioning:

  • Place the glass heaters inside the tank carefully. Remember that any strong contact with the glass or decorations inside the aquarium can fracture the glass.
  • Always turn the heater off and unplug it before changing the water. You should also unplug it while changing the position of the heater or the aquarium.
  • Do not buy a cheap heater by any means. These are made of bad-quality plastics and electrical components. As a result, the heaters may overheat and cause smoke.
  • If the tank is big, I recommend you to use two heaters or use a heater with more power. A single heater may go through a lot of pressure if the tank is too big or the power is too low.
  • Do not turn the heater on before putting it inside the water. For proper safety, turn it on after submerging it for 20 to 30 minutes.
  • Always use an external thermostat to inspect the temperature of the water inside the aquarium. Do not raise the temperature level above the suggested level for fast heating.
  • If you notice that the heater is not turning off, inspect the power button. Fix or replace the button if it has gotten stuck permanently.
  • Do not let the water level become too low. It is very dangerous for a submersible heater to stay out of water.
  • Buy a new heater if it has gotten too old.
  • Use a heater controller along with the heater for a safer heating system.

It is always better to prevent the aquarium heater from smoking. The heater may explode and the fish may get harmed if you fail to follow these tips.

Should I Fix Cracked Aquarium Heater Due to Overheating?

If the heater has developed a crack due to overheating and smoking, you should refrain from using it immediately. It may break or explode at any point if you continue to use it.

If you see any obvious damage to the aquarium heater’s glass, it is usually advised to get a new one.

Adhesive repairs won’t prevent it from overheating once more. The effect is that the water will combine with the dissolved adhesive. The fish may perish as a result of toxic adhesives.

A damaged heater should never be used since it might burst and the fish could get hurt from the sharp glasses.

The chance of electrocuting the water increases while using a broken heater. The electrical components might become wet. You or the fish might suffer from an electric shock in this way.

How to Cure a Fish Burnt by an Overheating Heater?

The skin of the burned fish can be treated with salt. Act quickly before the harm is irreversible.

You should add 3 grams of salt per liter of water. To stop the virus from spreading, you should also use a topical fungicide.

It will take a few weeks for the wound to completely heal if it is not deep. It will take longer for a deeper wound to heal.

Allowing the wound to heal naturally is another option. The fish will gradually cure itself if the burn is only a little and hardly noticeable.

What Are the Best and Safest Aquarium Heaters?

You should buy a great quality heater along with maintaining the heater correctly. Here are some of the best heaters with safety features:

  1. Fluval E200 Advanced Electronic 100-Watt Heater
    – Features a dual temperature sensor for precise reading.
    – Integrated safety shutdown technology with heater protector.
  2. Hygger Aquarium Heater with Thermostat Controller and Thermometer
    – Has a quick heating option for pre-heating before adding fish.
    – Stops heating when it reaches the set temperature preventing overheating.
  3. Orlushy Submersible Aquarium Heater
    – Available powers: 30W, 50W, 100W, 150W, 200W, 300W, 500W
    – Adjustable from 20 to 32 degrees Celsius.

You can also use these products to prevent overheating and smoking:

  1. Dovewill Aquarium Heater Protector + Suction Cup
    – Has a six-section detachable design to fit any size of aquarium heater.
    – The dimensions are 1.02 x 16.73 inches.
  2. BN-Link Digital Cooling Thermostat Controller– It is easy to operate using three buttons and easy to read the display.
    – Can be used along with an aquarium water heater to prevent overheating.


The aquarium heater is a key component for keeping fish safe in cold weather. However, if the heater is used irresponsibly, it might overheat and start to smoke.

While changing the water and the heater’s position, always turn the heater off. Use the safety equipment I have recommended as well.

I have covered a wide range of causes and mitigation strategies for aquarium heater smoking and overheating. To prevent any form of accident, carefully follow my advice.

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Arif H Fahim

Welcome to PetFishTank! My name is Arif. I make an effort to publish educational articles using my many years of expertise as a fish owner.

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