Aquatic creatures living in an aquarium appreciate a little heat. If you can keep the tank water between 76 to 80°F, you’ll make most species happy. And the easiest way to maintain the temperature is with an aquarium heater.
In general, you can use the size of your fish tank to determine the wattage of the heater you need. For example, a 5-gallon tank would need a 50-watt heater to raise the water temperature between 5 and 15 degrees F., But a 20-gallon tank could use either a 50W or 100W heater, depending on room air temperature. The more water you need to heat, the more powerful of an aquarium heater you’ll need.
Top aquarium heaters
Let’s take a look at the best aquarium heaters for a variety of tank sizes. Then at the end of the article, you’ll find tips on managing the temperature of your aquarium water.
#1 Aqueon Pro Adjustable Heater
Aqueon’s Pro Adjustable Heater is very popular because it’s inexpensive and easy to use. It has an adjustable temperature setting that works well for different kinds of fish whether they prefer warmer or colder water. It also comes in a variety of wattages like 50W, 100W, 150W, 200W, and 250W.
The heater is fully submersible and shatterproof. It comes with three suction cups for mounting in either a vertical or horizontal position. Then, on the top is a knob that you can turn to set a temperature between 68 to 88°. And its built-in thermostat is accurate to plus or -1°F.
When it’s heating the water, the LED light is red. But when it’s not increasing the temperature of the water, the LED is green. Should you ever have a problem with the heater, Aqueon offers a limited lifetime warranty.
#2 Cobalt Aquatics Neo-Therm Aquarium Heater
The Neo-Term series of heaters from Cobalt Aquatics suits aquariums from 6 gallons up to 55 gallons in size. They come in 50, 75, and 100W sizes.
This European-made slim-style heater has an electronic thermostat and an LED display. The display shows the temperature you’ve chosen as well as the temperature of the tank water at the same time. You can raise the temperature up to 96°F.
Cobalt Aquatics includes thermal protection circuitry against overheating, and they offer a three-year warranty.
#3 EHEIM Jager Aquarium Thermostat Heater
EHEIM Jager makes their aquarium thermostat heaters in Germany. They come in a variety of wattages like 50, 75, 125, 150, 200, 250, and 300-watts for an assortment of tank sizes. And they are appropriate for both freshwater and saltwater aquariums.
The tubes are built from laboratory-grade shatterproof glass. They have a dial that allows you to adjust the temperature between 65 to 93°F. The accuracy has been tested to be plus or minus half a degree Celsius. And the EHEIM Jager heaters are unique in that you can recalibrate it to make sure it’s as precise as you need it to be.
Each heater also has Thermo Safety Control, which means it will automatically shut off when removed from the water, then resume functioning when submerged. And the indicator light reveals when the heater is working.
Of course, the heater comes with a mounting bracket and suction cups. And the manufacturer reveals that the power cord is 5.6 feet long.
#4 FLUVAL E 300 watt Advanced Electronic Heater
The E-series of Advanced Electronic Heaters from FLUVAL is a pro-grade tool. It has an LCD screen that shows real-time water temperature in both Fahrenheit and Celsius, with a range of 68 to 93°F. And it has a colored display alert system to warn you if water temperatures are varying from the setting you selected.
In other words, the display will flash red if the aquarium temperature rises more than 5.5°F over the temperature you chose. And you can set your preferred temperature in 0.5° increments.
Also, with an eye to protecting fish and invertebrates, the heater core is shielded against direct contact so it won’t burn them. And the glass sleeve is strong enough to resist bumps and bangs from large fish.
Fluval sells the E-series heaters in four sizes: 50 Watts for aquariums up to 15 gallons, hundred Watts for aquariums up to 30 gallons, 200 Watts for aquariums up to 65 gallons, and 300 Watts for aquariums up to hundred gallons in size. Each one comes with a five-year warranty.
#5 ViaAqua 300-Watt Quartz Glass Submersible Heater with Built-In Thermostat
ViaAqua’s Submersible Heater comes in two sizes, 200W and 300-watts. Their ceramic heater cores are surrounded by waterproof double insulation and durable quartz glass.
Both are suitable for saltwater or freshwater aquariums. And both have a visible temperature setting as well as an indicator to show when they’re actively heating the water.
#6 Marineland Precision Heater for Saltwater or Freshwater Aquariums
Marineland’s Precision Heater is also made for saltwater and freshwater aquariums. You can buy it in a variety of wattages, from 50 to 400-watts. For example, the hundred and 50 W version is designed for aquariums up to 40-gallons in size.
The adjustable temperature dial changes in temperature 1° with every click. And the sliding scale shows you the exact temperature setting you’ve chosen. Or you can view the temperature from the top down position.
It comes with a mounting bracket that allows you to choose one of three positions so that you can easily view the temperature display.
Just one word of advice, as much as we admire other products from Marineland, we were discouraged by the number of negative reviews for this one. It appears that several people had the heater fail in the past.
#7 Finnex Electronic Controller Aquarium Titanium Tube with Heater Guard
If you want a top-of-the-line heater for your tank, try the Finnex HMA Series Heater that has a titanium tube and electronic controller. In some ways, it’s superior to a glass tube heater. As they describe it, it’s corrosion-resistant and almost unbreakable. Plus, you can buy the wattage you need between 100 and 800-watts.
This compact heater maintains water temperature within plus or minus 2°F of the value you choose. It heats very quickly and has an LED light to show you when it’s working. And the heating element is isolated by a protective guard to make sure it doesn’t damage the tank inhabitants or other equipment.
#8 Marina Compact Heater
Marina’s Compact Heater is tiny, the perfect size for aquariums up to 2.65 gallons in size. It maintains a set temperature of 78°F and works well in either fresh or saltwater aquariums. Should you have any problems, Marina offers a 2-year warranty.
The 10W heater doesn’t need any adjustments on your part. And when it says 78°F, what it means is that the heater itself maintains its own temperature at 78°. Your water temperature may vary based on the ambient temperature of the room where the tank is located.
#9 Hydor Slim Heater for Bettas, Bowls and Aquariums
The Hydor Slim Heater for Bettas and Bowls is basically a heating pad. You can purchase it in 4, 7.5, and 15W versions. Then simply position the bowl on top of the pad and turn it on. The manufacturer says that it’s capable of maintaining the water 5 to 10° warmer than room temperature, based on the wattage of the heater you use and the size of the aquarium.
#10 Marina Betta Submersible Heater for Aquarium
The Marina Betta Submersible Heater looks a lot like a keychain car remote. It’s fully submersible and designed for aquariums up to 1.5 gallons in size. In other words, it’s perfect for betta fish.
The 8W heater is encased in polymer which is more durable than a glass sleeve. It has a red indicator light that illuminates when it’s heating the water. And it comes with a suction cup to secure it against the side of the tank or bowl.
#11 Cobalt Aquatics Mini-Therm Heater, 5 watt
Cobalt Aquatics also sells this mini heater with 5W of power, enough to raise the temperature of a 1.2-gallon tank 10 degrees. Inside its thermoplastic polymer shell is a ceramic heat radiator. And you can submerge it fully in fresh or saltwater aquariums for terrariums.
#12 TetraFauna Aquatic Reptile Heater for Frogs, Newts & Turtles
We know that it’s not only fish that live in aquariums. Frogs and turtles need heat too. And the TetraFauna Aquatic Reptile Heater has 100-watts of power to keep 30 gallons of water at a balmy 78°.
The compact heater comes with two large suction cups to keep it in place. And it also has an 8-foot-long power cord for convenience.
How to manage the temperature of the aquarium water?
Now that you’ve seen a variety of the best aquarium heaters for your fish tank or terrarium, let’s discuss how you can manage the temperature of the water.
Besides a heater, it’s essential to have a reliable thermometer. Some of the heaters in our review today come with their own thermometer. It’s still wise to have a second thermometer to verify the accuracy of the heater.
Next, most fish appreciate temperatures from 76 to 80°F or 25 to 27°C. Of course, some prefer warm water, and a few prefer colder water. If you’re not certain what’s best for your future aquarium inhabitants, do a little research before you bring them home.
While some aquarium heaters have a simple on-off design, others allow you to select the temperature you desire. But this is where things get tricky, and why you need a separate thermometer. For example, you might set the heater to work at 78°. But the heater may bring its own core temperature up to 78°, without adequately heating the water to 78°.
But that’s not the only problem you have to manage. Next, the temperature of the room will affect the temperature of the water in the tank. And if the tank is exposed to sunlight or other heat sources, that has consequences, too.
To avoid problems with overheating the tank, you might opt to spend a little more on a better heater with a thermostat. After all, if you are paying all that much money for your fish, the tank, and the accessories, what’s a few dollars more to make sure everything runs as it should and the fish stay healthy?
Next, it’s smart to put the heater where the water flow helps circulate the warm water around the tank. This might be near the filter or the sump.
Finally, let’s talk about how to cool down the water when it gets too warm. First, increase the movement of the water because that will increase the amount of oxygen in it, and it also speeds the amount of evaporation, which will cool the water. When the water is warm, it raises the fishes’ metabolism, and they require more oxygen.
Although more evaporation means having to replace tank water more frequently, it can help your fish feel more comfortable. And if the tank is in a place where the room air is quite hot, you might need to invest in a chiller.
As you have seen, the best aquarium heaters come in a variety of sizes and wattages suitable for any size tank. From the smallest Betta bowl to tremendous 100-gallon tanks, you can find the perfect heater for your setup. Take the time to choose one that will let you rest easy knowing that your aquarium inhabitants will be healthy and comfortable.