Aquarium Heater Introduction

A quality aquarium water heater is necessary if you intend to maintain a successful tropical freshwater, marine fish or reef system. Temperature fluctuations often go unnoticed by aquarists and can cause stress to fish and corals.

Most fish tank heaters include a built-in thermostat to select the optimal temperature for your aquarium, however, the use of a thermometer to monitor the temperature is highly recommended. You might consider a temperature controller for keeping a stable environment in your aquarium since they offer more precise readings and a more advanced feature set.

A minimum of 3-5 watts per gallon is recommended to keep aquarium temperatures at an optimal level. Aquarists with larger tanks should consider using more than one heater. In the unlikely event that your heater goes, have multiple heaters in place safeguards your tank from crashing.

For more information about aquarium heaters and to read product reviews, please visit our website:


mohawk1069 says:

Video summary…. Heaters are good.. You may need 2.. You can buy them at Marine Depot… roll credits…….

Marine Depot Aquarium Supplies says:

The general rule of thumb for heaters is 3-5 watts per gallon. For a 300 gallon aquarium, you will need at least 900 watts and up to 1500 watts total. You can accomplish this by purchasing multiple heaters, which will also give redundancy. We recommend the Eheim Jager brand heaters.

88MVELA says:

Thanks alot man i really appreciate ur help..

marioACWW says:

Is the hydor 25 watt heater good for a 3 gallon betta tank? Im planning on buying it . I dont like preset heaters because the always stay on and i dont want it to always fluctuate.please marine depot answer thank you .

James says:

Are all of those heaters totally submersible under water ?

Marine Depot Aquarium Supplies says:

The Hydor Slim Heater supplies Continuous Safe Gentle Heat that increases the temperature in small aquariums or bowls, approximately 5 to 10 degrees above ambient room temperature. There are no glass components to crack or break and double sealing the heating element makes these units the safest heaters on the market. For further information please contact us directly at 1.800.566.3474

Alex Paulsen says:

I’m using 2 x 200w heaters in a 180 litre aquarium (47 US Gallons). A single 200w heater on it’s own wasn’t doing the job properly, but overnight temperature drops here in winter (Only as low as 0 degrees Celsius) have me convinced even 2 heaters isn’t sufficient. I went from 26 degrees to 23.9 degrees overnight, but the thermostats on my heaters didn’t even give a hoot. I’ve been using both a digital and mercury thermometer at opposite ends of the tank, and they both give me similar figures.

Now I’m considering a layer of foam on the back of the aquarium… and doing a lot more research about heaters.

Marine Depot Aquarium Supplies says:

Much of this will depend on the ambient air/water temperature in your garage. For a 10 degree increase in water temperature, 3-5 watts per gallon is recommended. For a 20 degree climb in water temperature, 5-10 watts per gallon is recommended.

suraj khanvilkar says:

have we can on a heater in summer for flowerhorn

LokuKina says:

I have a 1500 watt Jehm co., is this a good heater or not? I have not used it yet, but thought to ask around. It is a titanium heater, and I have a 300 gallon structural foam tank.

jackson jones says:

Hey mate I need help and a polio Please I currently have 1 frugal 300 watt heater in my 75 gallon tank it doesn’t seem to be keeping it at the correct temperature I set it between 78 and 82 for african thing is I have a 50 watt aqueon submersible heater in my 10 gallon tank and it stays warm. Would u think 2 150 watt aqueon heaters would be better spaced in 2 different places in the tank and oh my tanks are in the basement in the winter it gets really cold and in the summer it gets really hot in the basement please help asap thanks

88MVELA says:

Im setting up a 300g witch one do u recomend thanks …

SimplicitySims says:

What would you suggest for a 1 gallon glass bowl? It has flat sides in the front and back and the two sides are more rounded.

Ali Mohamed says:

dear friend,

thanks for such important info.

i have the following question

im planing to make a 800 gallon fish tank. as i understand that for heating a tank it should be 5 watt per gallon so i need 4000 watts. if i plan to go with true temp heater, do i need to buy a TT 1000 x 4?

and to adjust them all to the same temperature?

can you help me please.


Marine Depot Aquarium Supplies says:

It’s tough because it’s round. For a 1-gallon aquarium, try the Cobalt Aquatics Mini-Therm Aquarium Heater which is rated for tanks up to 1.2 gallons. The Hydor Slim Heater would work, too.

vivek tawre says:

hi friend i am leaving in india in india water heater is necessary or not

mersf559 says:

what heater do you recommend for a 2 gallon fluval spec? im not sure if ineed one since it is the summer in my area but my temp jumps from being 76 in the morning to 80 later in the day

Emily Romo says:

I have a 50w water heater and it has a little light in it and it turns off by itself does that mean the water is the temperature its supposed to be or is it broken

David George says:

]’m imagining the dense fog bank frank1971ification is going to have in his garage, Have you ever seen video of Japanese Snow Monkeys lounging around in how springs surrounded by ice? Good luck Frank!

frank1971ification says:

please reply back. I got 4 Jäger TruTemp 300 Watt Heaters rated at 159-264 gallons for each one. my question is would 4 of these be able to keep my turtle tank over the winter in my garage at a warm temperature. P.S I live in Canada and my tank has 80 gallons of water in it.

Marine Depot Aquarium Supplies says:

Hi marioACWW. Thanks for watching our video! A 25-watt heater from a reputable brand like Hydor will work just fine for your betta tank. We generally recommend 3-5 watts per gallon, so you’ll be good to go with that choice. If you have any additional questions, feel free to let us know!

Marine Depot Aquarium Supplies says:

It appears the one our staffer is holding in the beginning and end of the video is an inline heater which is designed for vertical use outside (externally) of the aquarium. Inline heaters are a nice choice if you want less equipment visible inside the aquarium. The flat looking one is a mini heater for small 5-10 gallons tanks, though it’s still an internal model. If you have any more questions about heaters, like what might be a good choice for your specific tank build, please let us know!

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