Eric is an aquarium enthusiast with over two decades of experience caring for a wide array of tropical fish.
Choosing an aquarium heater may not seem like a major deal, but pick the wrong size or brand and you could end up with some problems in your fish tank. Choose one that's tough to work with and you're going to find yourself frustrated and annoyed.
In this article I'll tell you about what I look for in an aquarium heater and how to make the best choice you can for your tank. It's a mistake to pick up a cheap heater and expect it to do the job.
I can't even imagine how many different aquarium heaters I've used over the years. Some were good, and others really, really bad. Perhaps you can learn from my mistakes!
Along with a good filter, the heater is among the few pieces of equipment your fish need to stay healthy. Taking a moment to make a smart decision here can pay off down the road, and a little research and reading can potentially save you from some major headaches.
What I Look For in a Heater
So, what separates a good aquarium heater from a bad one? When I consider a heater for my fish tanks, I look at a few factors:
- It must be adjustable. This may seem like a no-brainer, but there are some heaters on the market that are pre-set for a certain temperature. You can't adjust them. I avoid these, because if you need to raise or lower your tank temperature there is nothing you can do about it. I'd rather a heater with a thermostat I can control.
- The control knob must be easily accessible when the heater is in the tank. Some of these things seem like they were made by people who never owned a fish tank in their lives. The better ones will have a nice, big control knob that's easy to grab and twist when the unit is in the water.
- I want to see some type of numbered system, either on the control knob itself or another readout. It's nice if it tells me what temperature the heater thinks it's set at, but any numbers for reference are fine. Keep in mind that just because your heater thinks it is set at a certain temperature doesn't mean the tank water will necessarily be that temperature. You still need a separate thermometer so you can make adjustments.
- Ideally, I'd like a readout I can easily monitor from the front of the tank. A top-mounted readout isn't a deal breaker, but it's much nicer to be able to see the readout at a glance.
- Safety features: It should be fully submersible. This is pretty common, but watch for it anyway. Another useful feature is an automatic shut-off in case the water level suddenly drops. Shatter-proof and shock-proof are some other words you should look for when choosing your heater. Read the specs of any heater you are considering and look for these features.
My Top Choices
I've compiled my three best picks for aquarium heaters based on my own experiences and research. They come in different sizes and power ratings, from heaters that are appropriate for small 5-gallon tanks, all the way up to heaters for 55-gallon aquariums. There are even some heaters that are appropriate for 75-gallon tanks and larger.
Always read reviews carefully when choosing your heater. Look for cases where defects in the heater caused major issues for aquarium owners. I'm not talking about people complaining the heater was off by 5 degrees. I mean cases where heaters cracked, exploded, or heated the water uncontrollably.
In fact, there were a few brands I've had good experiences with but didn't feel comfortable recommending based on other people's stories. I tried to keep the options affordable while approaching the criteria I outlined above, but remember that quality is important in a key item like your aquarium heater.
Here are three heaters I recommend checking out:
1. Cobalt Aquatics Neo-Therm
Cobalt Aquatics is a brand with some innovative ideas, and I particularly like their Neo-Therm heater. Here's a fantastic heater that meets all of my criteria and then some.
Firstly, it's shatter-proof, so no worries of cracked glass or similar disasters, and it has thermal protection circuitry.
Setup is super simple: Install the Neo-Therm and it will sense your tank water temperature. Then, use the "One Touch" system to set your desired temperature. According to Cobalt, the Neo-Therm will maintain your water temperature within half a degree. Impressive!
The readout is easy to view from outside the tank, which I really appreciate, and it can't be much easier to set than the "One Touch" design. Even though the thermostat seems very accurate on the Neo-Therm, I'd still use a separate thermometer to gauge water temperature.
The Neo-Therm Heater from Cobalt Aquatics
2. Eheim Jager Aquarium Heater
Eheim is a German brand with a good reputation in the aquarium industry. I like that this heater is fully submersible, and has an automatic shut-off should the water level drop. Nice!
Even better, via the TruTemp dial you can calibrate it to more precise temperature settings, so it's about as accurate as you can get. I still suggest using a separate thermometer to keep track of the temp in your tank, but this heater is pretty good when it comes to keeping the right temperature.
The Eheim Jager heater is also made from shatter-proof, shock-resistant glass. There are some real horror stories out there about what can happen with a low-quality heater when they crack. Choosing a well-made heater like this one will set your mind at ease.
Note that the temperature reading is in degrees Celsius, so we Americans may need to do a little math. But that still provides reference numbers for adjustment. You should be monitoring your water temperature separately anyway!
3. Aqueon Pro Heaters
Aqueon Pro aquarium heaters feature a big, easy to adjust knob on top with a clear temperature setting indicator. I've had some pretty good experiences with Aqueon products. I've found them to be accurate and durable and have used them in freshwater tanks as well as brackish setups.
They are made of shatterproof material, and they're fully submersible, which are two big points in my book.
The Aqueon Pro also has a red/green indicator light, letting you know if your aquarium is at the right temperature. This is one of my favorite features of this heater, as many heaters simply have a red light that lets you know whether the thing is working or not.
You know what I am going to say next: Use a separate thermometer anyway!
What Size Is Best?
There are various "rules of thumb" floating around out there when it comes to choosing the correct heater size.
One thing I've noticed about aquarium care over the years more than any of my other hobbies: Rules of thumb have the potential to get you in a lot of trouble!
The main concern here is choosing a heater too powerful for your tank size, so underestimating is better than overestimating.
Instead of guessing, check the manufacturer's recommendation for the individual heater. They should be able to tell you exactly which heater is right for your tank.
Remember that there is more to choosing the right wattage heater than tank size, so math and "rules of thumb" only help you so much. Your ambient air temperature will play a part in how hard your heater needs to work, as will the flow rate of your filter and even the strength of your lighting.
After you install your heater, monitor your tank to make sure the temperature is staying in the correct range. For tropical fish you're aiming for 75-80 degrees (I shoot for 78, to be exact). Once you know how the heater is performing in your specific environment, you can make adjustments as needed.
It's true for temperature as well as many other aspects of aquarium care: By closely monitoring your tank you often can stop problems cold before they get out of hand, and prevent the heartache of losing your fish.
A bad heater can literally destroy your tank overnight. You could cook your fish, electrocute them or if the heater cracks and water seeps in, it could explode. Such happenings are rare these days, but choosing a quality heater makes a big difference and offers a little peace of mind.
Always keep an eye on any new heater you install in your tank. Monitor the water temperature independently and make sure everything is okay. Even a good aquarium heater may have a rare defect.
Good luck choosing your new heater, and in keeping your fish happy and healthy.
Tank Size Matters!
ngrrsn on January 14, 2016:
Helpful article, but no home heaters have yet to meet my criteria --- simply, a fail-safe fuse to prevent cooking your fish. It must be separate from the unit "off/on" thermostat. Even excellent brands can stick "on" and kill your fish overnight, even those with "auto off" because they are linked to the units thermostat switch. I want a heater that has a separate fuse, not tied to the units thermostat, that will automatically fail (break the power circuit) if temp gets over a certain value. And, wouldn't it be awesome if you could choose the fuse depending on fish you are raising; a 75, or 80 or 90, for example. I worry more about heaters sticking on than failing to turn on; if they fail to come on at the most the temp will drop to ambient (room) temps. If they fail to turn off, you find a bunch of dead fish floating in your aquarium! It has happened to me.
sheilamyers on July 24, 2014:
Anne: Thanks for sharing your experience. I also shop for these kinds of things at PetCo or PetSmart because if I'm not sure what I need, the employees are usually very knowledgeable about the products and very helpful.
Eric Dockett (author) from USA on July 24, 2014:
Thanks for the advice, Ann1Az2. I think no matter where you get your heater it always pays to do a little research so you know what you're getting.
Ann1Az2 from Orange, Texas on July 23, 2014:
I agree with you on the heaters that don't have any adjustments and automatically set the temperature. The thing I've found out about them is that they don't last over a year or two and you're out buying a new heater. I have a heater in my 50 gallon that I really like. I'm sorry I can't tell you the brand, but I bought it at Petco and it was on sale for around $50. It has a temperature setting on the top in large numbers and is submersible. What I like the most about it is on the front, it has a green light that turns red when it's heating the water. It's kind of cool to know that it's working.
Another thing I've learned is to be careful when you buy heaters at Walmart. They are not always of the best quality. They sell a lot of the pre-set ones that last only a year or two. Best bet is Petco, Petsmart, a fish place, or online.
sheilamyers on July 18, 2014:
Eric: Thanks as always for the advice and tips. Even though I've had my aquarium for some time now, I'm still learning better ways to do things.
Eric Dockett (author) from USA on July 17, 2014:
Hi Sheila! Yes, I prefer to have my heater placed vertically so I don't have to jam my arm into the tank to manipulate it. But there's nothing wrong with placing it horizontally at the bottom of the tank. It's easier to hide down there, and some people will say it allows the tank to heat more evenly. Personally, I think if the water flow around your tank is sufficient it probably doesn't make a huge difference. Just make sure the heater is fully submersible and made for horizontal placement and don't put it under the gravel unless it is made for that.
sheilamyers on July 16, 2014:
Thanks for the great information. I'll have to read the paper that came with my heater because I don't know if it has the automatic shut off feature. If not, I'll definitely get one of those the next time I have to replace my heater. Now for a question. Some people say it's better to have a submersible heater and let it lay on the bottom of the tank. Other people will say it should always hang on the side where you can easily access the control knob. Although I'd guess you'd hang yours because you like the easy to reach control, but what's your thoughts about allowing to lay on the bottom of the tank?