Especially durable. Adjustable temperature dial. Shock-resistant. Easy to install. Optimized for salt and freshwater. Stylish reflective coating. Available in 50 to 200-watt models.
Not completely submersible.
Simple installation. Selectable temperature dial. Automatically turns off when dry. Extremely durable. For fresh and salt water. Available in several 25 to 300-watt options.
Must be calibrated for best results.
Highly adjustable temperature dial. LED indicator lights when heating. Completely submersible. Rugged construction. Available in 50 to 300-watt models.
These are relatively pricy.
Reliably keeps water at a constant 78 degrees. Good for most tropical fish types. Bright LED on/off indicator light. Compact design to conceal. Optimized for 2-10 gallon tanks.
Only 1 preset temperature setting.
We recommend these products based on an intensive research process that's designed to cut through the noise and find the top products in this space. Guided by experts, we spend hours looking into the factors that matter, to bring you these selections.
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.
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.
Four main varieties of aquarium heaters are available: hang-on-tank, submersible, substrate, and filter.
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. Consider 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.
Submersible aquarium heaters are generally tube-shaped and can be fully submerged in the water.
Submersible aquarium heaters 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 choices.
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 find a basic submersible aquarium heater for around $10, but high-end models can cost as much as $150.
Substrate aquarium heaters, also known as "undergravel" heaters or "heating cable systems,” are placed under the substrate (sand or gravel) on the bottom of the tank.
Since under-gravel aquarium heaters sit beneath 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.
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.
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.
Here's the wattage you'll need by tank size:
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.
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.
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.
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.