Best Ways to Heat your Fish Aquarium

Written by Randy Martin

Tropical fish tanks both freshwater and marine, need to stay at a certain temperature to keep your fish healthy. I have done a lot of research on the best way to heat your aquarium, here is what I found.

Best way to heat your fish aquarium? Maintain the temperature of the room where you keep your aquarium. If the temperature is consistent and at a measurement recommended for the species you keep, then this is ideal. If you can’t keep the temperature consistent, or at the correct temperature, then you will need to use a heating device.

Let me explain further why I think relying on room temperature is ideal. I will also get into what kinds of heaters could be best for your situation if you need them.

Best way to heat your fish aquarium

Some fish need warmer waters than others. But all the tropical fish species need a consistent temperature, especially marine species. If the temperature is rising and falling all over the place you are going to have a lot of problems on your hand. At the very least stressing your fish out, and at the worst—well… Lets just say it will be bad.

Note: You would be better off to always have a heater on hand whether you actively use it or not, just in case.

Heating the room instead of the aquarium

So why do I consider room heating to be the best option?

Some aquarist have had issues with using aquarium heaters. From time to time the heating device has been known to malfunction. If it stopped heating and you weren’t aware of it, then the water temperature could drop too low for your fish, spelling disaster.

Worse than that with some heaters that have malfunctioned, instead of not heating anymore, they didn’t stop heating the tank. To the point that all the fish in the tank perished.

Checking the temperature of your fish tank should be a daily task. You need to catch early on if there is any big fluctuations in the temperature.

Now this doesn’t happen to everyone, and this doesn’t mean that all heaters are faulty and prone to malfunctions. But since it has happened, a lot of fish keepers are mindful of the no heater route if they can get away with it.

As technology gets better and manufacturers come out with safer equipment, things like this will hopefully become even less common.

Another obvious factor is price. Adding additional heaters to your tank will use more energy consumption. This is a small factor if you have one aquarium. But can be a big consideration for someone running many aquariums in their home.

So the question really comes down to this. If your room, basement, house or wherever you are keeping your tank at, stays at a consistent proper temperature for your fish at pretty much all times, then why would you need a heater? You might not need one.

For example I live in Arizona, and around the Phoenix area there are many homes that hardly fluctuate outside of the 78°F range. The homes have to be constantly cooled in the summer and don’t need much heating in the winter.

I know of people that have fish tanks in their living room in these conditions that don’t use heaters and they are getting by just fine.

Take a look at what kind of species you plan to keep. Research the environment they come from, and then take a look at the environment you will be keeping them in and decide if you can provide them with the living conditions they need without a heater.

That way you can avoid the extra risks and costs that come with using a heater.

However, if you can’t give your fish that consistency then you need a heater to help out.

Where I’m currently living right now up in the mountains of Arizona, I definitely need to use a heater. During the winter the temperatures fall way below freezing. Also I use a wood stove as my main heating source, that is highly inconsistent and can’t be relied on for pet fish.

I keep my aquarium in a room separate from the fire place so I don’t risk over heating. I heat that room with an oil based heater to regulate room temperature better and to aid my aquarium. Then I use a submersible aquarium heater for my tank. So I kind of work both approaches in my personal setup.

Chances are most people’s setup will require a heater, but it’s good to know that a heater isn’t a definite must-have in all situations. That way you can decide for yourself depending on your situation.


If you need an aquarium heater

I’m going to suggest a few different heating systems here and what you might need depending on your situation.

But be aware of your particular setup. You need the correct wattage of heater for the size of your aquarium. The general rule of thumb is 2 to 5 watts per gallon. If the room is heated then you don’t need as much power on your heater, but if the room is colder then you would need the full 5 watts per gallon.

Another factor to keep in mind is that smaller aquariums actually lose heat quicker.

A very important factor when heating your tank is working with your water flow. You need to make sure that the heat is being circulated through out your aquarium. If you have a submersible heater then this is a very important concept, I write in depth about the best place to put your heater for maximum benefit here.

If you aren’t circulating the warmth, then the heater’s thermometer will feel all that warm water directly around it and shut itself off thinking the correct temperature has been achieved, leaving the rest of the tank virtually unheated. This is why systems like an In-line heater have an advantage as they shoot the warm water into your tank via the filtration system.

A submersible heater and thermometer

Submersible Heaters

The heaters I use currently, that are probably used in most setups, are submersible heaters. There are some cheaper options out there, but the submersibles work so well and they aren’t expensive.

Since there was that risk that some heaters have malfunctioned on fish owners, and the fact that you are placing these directly into the water, I wanted to make sure I was getting the best one I could find.

I searched all over and after doing tons of research and receiving a lot of recommendations I kept seeing the Eheim Jager being raved about. You can find it on Amazon in every watt increment you could need, from the 25 watt to the 300 watt unit.

This is what recommend in my article about the Best heaters for your fish aquarium. There is many other good options there too.

There are people who have been running these for years without any problems at all, and they can really hold that temperature even in a cold room.

So there is a good chance that it will serve you well for a long time.

I would suggest to always have a backup on hand in case one does go out on you. You need to be able to slip in a backup quickly if your tank is dropping temperature.

Picking up two Jagers could be a good idea, or maybe look into this hygger submersible (on Amazon) so you can try out different brands. It has a unique look and comes with an external controller that you may prefer. One thing about it that attracts me is they designed it to be placed horizontally which is how I like them.

Marine saltwater tanks. The two heaters above can go in freshwater or saltwater aquariums. But if you do have a Marine tank or Reef tank then a hygger titanium tube might be a better fit for you. It’s pricier because of the anticorrosion elements and the hi tech controller. You could stick it in a freshwater setup to get real fancy too.

In-line heaters

Another option is to have an in-line external heater that connects to your canister filtration system. As I said one of the benefits of the in-line is that the warmed water will circulate better.

Another good plus from this type of setup is your tank will be less cluttered since you don’t keep it in the aquarium. So if you feel like having a heater inside your tank is an eye sore, then this can eliminate that for you.

People claim that they have had less malfunction issues with external in-line heaters too, but that doesn’t mean they are completely fail safe.

One of the in-line heaters I like is the ISTA inline external heater, they have it available on Amazon in 150 watts to 500 watts. So for example if you had a 30 gallon tank in a cold room that is hard to heat up, the 150 watt heater could work for you. Then of course you can use this with many tanks larger than that.

You can choose between 1/2″ and 5/8″ hose connection sizes depending on your canister filter. The controller is a nice digital display, but it’s only in celsius, that might be a deal breaker for you, but I think it’s a minor drawback if any.

You could also try out the Hydor external heater as an alternative, it’s popular and has tons of great reviews.


Always take a look at your situation and decide the best way to heat your fish tank. If the room where you are keeping them at is warm enough, then you are totally fine.

Just pick up at least one heater so you are always prepared. If your local fish store doesn’t carry a Jager or one of the other brands then I would head over to Amazon to look into those.

Related Questions

How to heat a fish tank without a heater? Keep the aquarium in a room with a well controlled temperature that doesn’t fluctuate. Research your fish species to understand what temperature they need. If you can’t meet that requirement or keep it consistent then you need an aquarium heater.

How do I know if my aquarium heater is working? Almost all modern aquarium heaters come with an indicator red light that will turn on when the heater is actively warming the water. You should check your aquarium’s water temperature daily with a thermometer.

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