Thermoplastic material means no shattered glass. Green and red indicator LEDs are helpful. Adjustable temperature gives users greater control over tank temps. Reliable, operating for years without a problem.
Some owners report that unit doesn’t heat accurately. Reports of parts corroding or rusting, mainly in hard-water environments.
Temperature presets and easy-to-read indicator are nice pluses, as is the calibration feature, users note. Heats larger tanks fairly well.
Reports that the unit can overheat past the set temperature. Temperature settings are touchy and calibration doesn’t always take.
Works well in smaller tanks, particularly for Betta fish. Simple to set up. Power cord is nice and long, owners note. Heats 5-gallon aquariums quickly, within 10 minutes.
Can fail or overheat without warning, some owners report. Preset temperature measures too low in some aquariums. Doesn’t work well in larger aquariums.
Users like the LED status indicator. Glass appears sturdy, and plastic protector keeps fish and turtles alike from being harmed.
Doesn’t hold correct temperature well. Operates erratically after a short period of use, some owners report. Water doesn’t flow fast enough around heater, reducing efficiency.
Owners like the quality of the fittings, and the way this alternative heating unit doesn’t clutter the back of the tank. Maintains desired temperature very well.
Owners must purchase separate thermostat to better monitor aquarium temperatures, and a canister filter.
We purchase every product we review with our own funds — we never accept anything from product manufacturers.
We purchase every product we review with our own funds — we never accept anything from product manufacturers.
Keeping aquarium fish requires specialist equipment, and a good aquarium heater is one of the tools of the trade. But which heater is right for you, your fish, and your tank?
If you're new to the fishkeeping world, there's a lot to learn, and aquarium heaters are just one of the things on your list. Even if you're an experienced aquarist, you'll often find new and improved technology, so it's good to refresh your knowledge now and again.
At BestReviews, our goal is to assist consumers in finding the best products. We test items in our labs, consult experts, gather feedback from existing customers, and do extensive product research. The result? Fair and thorough reviews that can help steer you through tough purchasing decisions.
Read on for our full guide to aquarium heaters. When you’re ready to make a purchase, take a look at the product list above to learn about our five favorite picks.
Not all fish require an aquarium heater, but many do. Coldwater fish, such as goldfish, thrive at lower water temperatures, so they don't need an aquarium heater unless you live in a very cold climate.
Tropical fish and marine fish, on the other hand, generally require an aquarium heater to keep the water in their tank at a suitable and consistent temperature. If in doubt, do some research to find out the water temperature requirements of your fish (or the fish you plan to keep).
Some species of fish have very precise water temperature requirements – for them, just a few degrees could mean the difference between sickness and health.
Consider the maximum comfortable temperature for your fish, as well as the minimum. If you live in a hot climate or experience a heatwave, you may need to switch your aquarium heater off during the warmer months to avoid overheating.
Four main varieties of aquarium heaters are available: hang-on-tank, submersible, substrate, and filter. Here we examine the pros and cons of each.
Also known as "hang-on" heaters, these units hang off the back of the tank, partially submerged in the water.
Hang-on-tank aquarium heaters tend to be inexpensive.
Because they're readily available and easy to use, hang-on heaters are popular with beginner aquarists.
Hang-on-tank aquarium heaters are less efficient than other varieties.
Ultimately, you'll find better options out there. We recommend a hang-on model only if you have no other option available to you.
Price: Low-watt hang-on aquarium heaters can be found for $5 to $10. Even very powerful models don't usually exceed $50 or $60.
A fully submersible aquarium heater gives you more freedom over placement, depending on your tank's size and configuration.
Submersible aquarium heaters are generally tube-shaped and can be fully submerged in the water.
Submersible aquarium heater are efficient at regulating water temperature.
You can easily find a wide range of submersible aquarium heaters online and in pet stores, so you have plenty of choice.
You can place a submersible heater either vertically or horizontally for even heat distribution.
Submersible aquarium heaters tend to be affordable.
Submersible heaters are more visible than some other types (like, for example, the substrate aquarium heater), and some people don't like this aesthetic.
Cheaper submersible aquarium heaters may have glass parts, which can break.
Price: You can buy a basic submersible aquarium heater for around $10, but high-end models can cost as much as $150.
Look for an aquarium heater with variable temperature control, so you can turn it up or down slightly depending on the room's ambient temperature.
Substrate aquarium heaters, also known as "undergravel" heaters or "heating cable systems,” are placed below the substrate (sand or gravel) on the bottom of the tank.
Since undergravel aquarium heaters sit below the substrate, they're not visible in the tank.
Substrate aquarium heaters promote plant growth, so they're the ideal choice if you have a planted tank.
Substrate aquarium heaters warm the water more evenly than most other varieties.
Substrate aquarium heaters aren't widely used in North America, so you may have less choice between models.
If you already have an established tank, you have to completely empty it and take out the substrate to install one of these heaters. However, this isn't an issue if you're setting up a new aquarium.
Price: You can find low-watt heating cable systems for small tanks starting around $15 to $20, but more powerful models cost between $50 and $100.
Submersible heaters are hard to fix should something go wrong with them, since they're completely encased in watertight glass or metal shells.
Filter aquarium heaters are a newer variety of heater that combines a filter with a water heater.
The two-in-one nature of a filter aquarium heater means you have only one item in your tank, rather than a separate filter and heater.
With a filter aquarium heater, the water is heated as it moves through the filter. It's already warm when it flows out, giving you excellent heat distribution.
Filter water heaters can't be damaged by even the most active of aquarium residents.
High-end filter aquarium heaters can be expensive.
Since filter aquarium heaters are newer technology, you have fewer makes and models to choose from.
Price: Basic filter aquarium heaters (that can be added to an existing canister filter) may cost as little as $30 or $40. Powerful all-in-one models can cost up to $100 or $200.
You can also buy "in-line" aquarium heaters, but they're one of the more uncommon choices, as they're only useful if you use a sump tank.
It's vital that you choose the correct wattage for your aquarium heater so your tank water is heated to the right temperature. The higher the wattage, the more powerful the heater. Therefore, the larger your tank, the higher wattage you'll need.
As well as the size of your tank (in gallons), you must work out how many degrees of heat you need to apply to your water. For example, if the average temperature in the room where you keep your aquarium is 65°F and the fish you're keeping require water of 80°F, you'll need to heat the water in the tank by 15°F.
If your heater breaks, your fish could die. Most people agree it’s worth spending top dollar to get a reliable aquarium heater from a reputable brand.
Here's the wattage you'll need depending on the above factors.
If you have a 5-gallon tank, you'll need a 25-watt heater to increase the water temperature by around 9°F, a 50-watt heater to increase the water temperature by around 18°F, and a 75-watt heater to increase the water temperature by around 27°F.
If you have a 10-gallon tank, you'll need a 50-watt heater to increase the water temperature by around 9°F, a 75-watt heater to increase the water temperature by around 18°F, and a 75-watt heater to increase the water temperature by around 27°F.
If you have a 20-gallon tank, you'll need a 50-watt heater to increase the water temperature by around 9°F, a 75-watt heater to increase the water temperature by around 18°F, and a 150-watt heater to increase the water temperature by around 27°F.
If you have a 25-gallon tank, you'll need a 75-watt heater to increase the water temperature by around 9°F, a 100-watt heater to increase the water temperature by around 18°F, and a 200-watt heater to increase the water temperature by around 27°F.
If you have a 40-gallon tank, you'll need a 10- watt heater to increase the water temperature by around 9°F, a 150-watt heater to increase the water temperature by around 18°F, and a 300-watt heater to increase the water temperature by around 27°F.
If you have a 50-gallon tank, you'll need a 150-watt heater to increase the water temperature by around 9°F, a 200-watt heater to increase the water temperature by around 18°F, and two 200-watt heaters to increase the water temperature by around 27°F.
If you have a 65-gallon tank, you'll need a 200-watt heater to increase the water temperature by around 9°F, a 250-watt heater to increase the water temperature by around 18°F, and two 250-watt heaters to increase the water temperature by around 27°F.
In large tanks, you may get more even heat distribution by using two lower-watt aquarium heaters instead of a single high-watt heater.
If your fish are particularly boisterous, consider using a heater guard to protect both the heater and your tank's inhabitants.
With a submersible heater, the tube should be about as long as your tank is high to allow for more even heating.
Titanium heaters can get hot enough to melt acrylic. Never position your heater so that it is touching the side of an acrylic tank.
A high-quality aquarium heater should come with some kind of warranty or guarantee in case of failure.
Q. Where in the tank should I position my aquarium heater?
A. The best place to position your aquarium heater is next to the filter outflow, as this can help distribute heat more evenly. However, if you have a particularly large tank, it's best to have two heaters, one placed on each end of the tank, so the water on the side farthest from the heater doesn't get cold.
We recommend owning a backup heater so you can quickly replace the old one if it breaks or malfunctions. If your fish are particularly susceptible to changes in temperature, this is especially important.
Q. Are aquarium heaters easy to clean?
A. If your tank is healthy, your aquarium heater shouldn't really need cleaning, but if in doubt (or if you notice a buildup of algae), you can give it a wipe over – with water only – when you clean your tank.
Q. How do I set up my aquarium heater?
A. How you set up an aquarium heater varies depending on the type of heater, the manufacturer, and the model. Check the instruction booklet that comes with your chosen aquarium heater to find out how to install yours.
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