Everything you need to know about Aquarium Heaters

In this article we will go through why do we need a heater? What size to buy? What is a good quality heater and how to extend the life of a heater?


In this article we will go through why do we need a heater? What size to buy? What is a good quality heater and how to extend the life of a heater? Heater is one of the most component or accessories for an aquarium it can make or break your fish tank. If there are problems with your heater it can kill your fish so please invest on a good heater and dont look for a cheap one. Cheap ones will only last for 6 month or a year and will give out the right temperature as well.

Why do we need Aquarium heater?

It is recommended to keep a heater for your tank if you stay in temperate climate and if you have varying temperatures during day or night or during cold seasons.

If the fishes you keep are from tropical regions like Asia or South America, it likes warmer temperatures so you would need a heater for sure.

If you are using room heaters or AC then use a thermometer to measure the water temperature, if your water temperatures is stable at 75 F to 79F (24C to 26C) then you can avoid heater but regular monitoring would be required to ensure that the temperature doesn’t drop and fishes don’t die to sudden change in temperature.

It is important to understand that at colder temperatures you will see lot of diseases propping up like white spots or infections so important to keep an optimal temperature for the fish.

Is the heater required only for day or night?

The heater should be turned on all the time irrespective of day or night. Temperature fluctuations can happen at any time so it is important to keep it turned on. This will help to avoid fish stress or death.

Since the most of the heaters comes with inbuild thermostat, you can just set the temperature and it will automatically turn on or off depending on the water temperature.

It is important to buy a thermometer along with heater as it will tell us if the heater is working properly or not. Sometimes the heater might show that it is turned on but water is not getting heated this could either be due to heater not functioning properly or how the heater in positioned in the tank?

How to size the heater for your tank?

LitresGallonsWattsMy recommendation
75-12020-321501*100w & 1*50w

It is always recommended to buy a smaller size heater than the exact the numbers given above what I mean by that is, if in case you need a 100w heater buy couple of 50w heaters as this will say you money in terms of electricity bills as well as save on heater cost.

Heaters will fail so if only one heater fails then you will still have the other one functioning in the tank it will save the cost of replacing a single 100w heater and also save your fish as the other heater will be working. You will then only need to replace one 50w heater.

How to extend the life of your heater?

  • Understand how to fix the heater in the tank.

The heater should be fixed almost in the middle in a slanted position. Others once the water is heated, the heat will just rise and only heat the water surrounding the heater, this will lead to constant fluctuations in the heater and the heater will constantly turn on or off within few minutes.

Always ensure the top of the heater is outside the water, if in case the water keeps going into the temperature control unit it might get stuck in future and it will stop functioning. This is also caused due to water hardness.

  • Adequate flow around the heater

Ensure adequate flow of water around the heater so that the heated water can move around and heat is dissipated throughout the tank, otherwise only one side of the tank will be heated. Multiple heaters suggested earlier also helps in this cause of heating the water at all corners of the tank.

Whenever you are doing tank maintenance ensure that you are taking out the heater and cleaning it as well, if you have hard water in your house well or supply it will have white deposits due to salts (calcium carbonates)

  • Ensure all electrical equipment’s are turned off during tank maintenance

Majority of the heater failures happens because people forget turn off heater or other equipment during tank maintenance.

Whenever the heater is turned on and coil part of the heater is exposed, heater will burst and the glass will be broken. The only option is to change the heater.

Always buy a good quality heater

Hobbyist most of times buy cheap heaters from the shops or online thinking it is a good one as it is cheap and thinking they will invest on an expensive one in the future. They don’t consider heater as an important equipment for their tank.

Please note that cheap glass heaters will burst and will cause fish death and also will give your electric shock so please beware of the cheap ones you buy.

It is important to invest on a good quality heater, I would recommend Eheim heaters as they are one of the oldest brands out there and very reliable. There are other new age digital heaters which are good as well like Fluval and Aquael as they don’t have any glass surface.


It is always to important to have a heater for your tank as it will keep your water temperature stable and avoid fish death or stress. If you are having a planted tank ensure you keep temperature between 75 F to 79F (24C to 26C) as this will keep plants healthy and any temperatures beyond that will lead to plant death or wilting. Good temperature is also important for tropical fish so please have a heater to keep them healthy and lively and you will thank me later on for this advice.

If you still have some doubts, please do reach out to me at




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