Which Is The Best Aquarium Heater On The UK Market?

Some coldwater fish species like rainbow shiner and cherry shrimp don’t need a heater as long as you maintain the room at a stable temperature.

However, if you have tropical fish in your aquarium, a heater is a must-have. Tropical fish thrive in temperatures between 24°C and 27°C. You’ll need a heater with an internal thermostat that keeps the aquarium at a constant temperature.

In this buying guide, we recommend the best aquarium heaters you can buy online in the UK. We also have a few pointers on what to look for when shopping for an aquarium heater.

If you are in a hurry, please see below a quick summary:

Best Aquarium Heaters (UK Market)

Key Considerations When Choosing an Aquarium Heater

A. Wattage

Wattage is the most important feature to consider when buying an aquarium heater. Wattage determines the amount of water – and thus the size of aquarium – that the heater can heat comfortably and efficiently.

Oversizing or undersizing an aquarium heater are both bad.

A heater with wattage that’s too small for your tank will struggle to keep water at the right temperature, and will likely stop working before long. But the biggest danger is the water temperature dropping too low and threatening the life of your fish.

A heater with a wattage that’s too high is a waste of energy. A too-powerful heater can also be potentially dangerous for your aquarium if it breaks and doesn’t stop heating when the water reaches the right temperature. It’ll quickly overheat the water, putting your fish in danger.

Here are the best wattages for different aquarium sizes. Note that these are just general recommendation. Max capacity varies among different brands, even those with the same wattage.

• 4-30 litres – 25W
• 23-45 litres – 50W
• 45-90 litres – 100W
• 68-135 litres – 150W
• 90-180 litres – 200W
• 135-270 litres – 300W

As you can see, each wattage covers a pretty wide range of fish tank capacity. To further narrow down the ideal wattage, consider by how many degrees you need to raise the water temperature.

Subtract the room’s average temperature from the target aquarium temperature. For instance, if the room stays at around 20°C and the target fish tank temperature is 24°C, you need to raise water temperature by 4°C.

In that case, you can be conservative with the wattage. For a 90-litre aquarium, a 100W heater will do. But if the room is colder than 20°C, go with a higher wattage. For a 90-litre fish tank, a 150W or 200W heater is ideal.

If the room temperature is similar or slightly higher than the ideal aquarium temperature, you don’t need a heater. In fact, you may need an aquarium chiller if the room temperature climb too high.

B. Type of Heater

Submersible heaters are the best. Because both the heater and thermostat are underwater, the aquarium stays uniformly warm without hot or cold spots. A submersible heater will also do a better job keeping the aquarium at a precise temperature range.

On the downside, submersible heaters don’t last long.

External heaters have the control module outside the tank (hang on the tank or some other surface), with only the heating coil or tube going into the water.

To ensure uniform and accurate heating, we recommend getting an external heater with a separate submersible probe that monitors water temperature.

The main advantage of external heaters is the ease of monitoring and adjusting aquarium temperature. Most of these heaters have a large display that shows the current temperature.

C. Temperature Range

The typical temperature range for most aquarium heaters is 16°C to 32°C, which covers the ideal temperature for most fish and coral aquariums. Here is a selection of thermometers that will help you check the temperature.

D. Indicator Light

It’s a small thing, but an indicator light showing the heater is on is a big deal. It gives you peace of mind, knowing that the heater is functional.

By monitoring the indicator light, you can also tell if you got the right wattage. If the light keeps going on and off frequently, the heater may be struggling to maintain a stable temperature. Buy a higher wattage heater or add a second heater at the other end of the aquarium.

E. Safety

Make sure the heater is safe for your fish. Many submersible heaters have a glass exterior that prevents fish from getting shocked or burned.

Another great safety feature is overheat protection, though you’ll find it only in premium aquarium heaters. This feature turns off the heater automatically if the water temperature rises beyond a certain point. This can save your fish if the heater breaks and keeps heating the water beyond the set temperature.

• Tip: When ordering an aquarium heater, also get an aquarium thermometer. If the heater is faulty and overheats the water or doesn’t heat it well enough, you won’t know if you don’t have a thermometer. A thermometer is an extra layer of security that ensures the heater is working as intended.

Having a thermometer also lets you test the accuracy of the heater. If, for instance, the heater happens to be a couple degrees off, you’ll know to set it a couple degrees higher or lower to achieve the right temperature.

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