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Best Aquarium Heaters for 2021

For some species of fish, it is a necessity for them to have a well-heated tank in order for them to thrive and stay healthy.

Fish cannot regulate their own body temperatures, and so for fancy finned friends more used to tropical Caribbean seas, a flat in Milton Keyes may not quite reflect the climate they need.

But tanks won’t heat themselves, and so a good quality aquarium heater is the only way to help them maintain their body temperature by keeping the water at a stable and satisfying level of warmth.

To help you find the right heater for you, we’ve delved into the world of tank warmers, reviewing the different types available, as well as dipping into all of their pros and cons.

From inline heaters to new-age submersible options, we hope this definitive list will help you find the perfect heating partner for your beloved barracudas.

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    Our Top Picks

    Image Product Details
    Fluval E Advanced Electronic Heater
    • LCD water temp display
    • Integrated fish guard provides advanced protection
    • Easily adjustable heater bracket
    Check Price
    Marina Submersible Pre-Set Mini Heater
    • Easy to access temperature changes
    • Impact resistant glass and guard
    • Huge choice in other power levels
    Check Price
    AquaEl Ultra Heater
    • Really accurate temperature setting
    • Super thin
    • Easy to set up
    Check Price

    The Top 10 Best Aquarium Heaters Reviewed

    Fluval E Advanced Electronic Heater

    Providing some of the most sought after and premium quality aquarium heaters on the market, Fluval’s electronic heaters are guaranteed to conjure up a tropical paradise in your very own home!

    These models from Fluval’s E series are currently their most technologically advanced heaters yet and come in varying degrees of power, from 50 to 300 watts, meaning you can power up pools from 20 to 300 litres!

    Equipped with a smart microprocessor monitoring system, Fluval’s product accurately records your tank’s temperature with dual sensor probes, while a precise temperature setting lever allows you to adjust the exact temperature in 0.5 degree increments.

    The combination of these features means there’s no way you’ll never not know the exact temperature of your tank water, with an LCD temperature display constantly keeping you on top of your tank’s heating at all times. Colour changes on the screen will indicate any drops or rises in temperature, and flashing risk screens will warn you of any critical spikes or chills.

    It’s everything you need to ensure the safety and well-being of your aquarium inhabitants!


    • LCD water temp display
    • Integrated fish guard provides advanced protection
    • Easily adjustable heater bracket


    • Weight: 481 g (200w)
    • Dimensions: 5.1 x 2.5 x 31.8 cm (200w)
    • Wattage: 50, 100, 200, 300

    Marina Submersible Pre-Set Mini Heater

    An easy-access temperature controller. Easy to read temperature settings. An impact-resistant glass design in case your fish happen to get a bit giddy when swimming.

    These are just some of the highlights of this mini heater. There is also a bumper guard for their safety, as well as a completely waterproof sealing to ensure it stays working throughout its lifespan.

    Despite its small size, it is mighty. The 50w Marina Submersible Aquarium Heater provides reliable heating for fresh or saltwater aquariums up to 38 litres, so you don’t need a huge heater which takes up all the space to ensure your fish are kept in the correct heated waters.

    The power cord is 1.8m long, which is generous as well.

    This heater may be mini, but don’t worry if you have to get something a little bigger and more powerful – the same heater is available in levels up to 300W, or as low as 25W too.


    • Easy to access temperature changes
    • Impact resistant glass and guard
    • Huge choice in other power levels


    • Weight: 181 g
    • Dimensions: 2.5 x 2.5 x 15.2 cm
    • Wattage: 50

    AquaEl Ultra Heater

    An advanced heater in an unbreakable plastic casing, this heater has a high-precision electronic thermostat, a built-in thermometer, and an overheat alarm.

    Because the casing is unbreakable, it is great for tanks with large fish or animals such as turtles, and it will also protect animals from the heat and eventual burns when getting too close. It is easy to use with a one-touch system, using a single control button with a range of LEDs around the edge which tell you everything you need to know temperature-wise.

    This heater operates with exceptional accuracy (+/- 0.25° C) so a constant temperature is maintained. The heat can range between 20 and 33 °C, which means it is great for treating diseases such as white spots. A built-in system will prevent it from overheating too.


    • Really accurate temperature setting
    • Super thin
    • Easy to set up


    • Weight: 405g
    • Dimensions: 48 x 29 x 165 - 48 x 29 x 210cm
    • Wattage: 25, 50, 75, 100, 150W

    HITOP HP-608 Submersible Aquarium Heater

    If you always feel like you deserve a little extra cherry on top of your cake when you make a purchase, there’s no better aquarium heater goodie bag than this HITOP HP-608 offer, with added sucker cup and stick-on thermometer included!

    And forgetting the bonus items for just a moment, the device itself ain’t half bad either!

    Safe for humans and animals, HITOP’s device boasts a quartz glass material that is actually 33% thicker than the standard seen in most tank heaters, rendering this model completely explosion proof! (That unfortunately just means it’s protected from the heater itself malfunctioning, not a grenade Mr. Bond!)
    A 10-slot multi-branched ceramic frame also takes up just an astonishing 11 inches of room, a smaller use of space than most brands, yet still packing a huge power punch when it comes to heating up your tank!

    With 100, 200 and 300 watt models available, HITOP covers a wide range of tank sizes from 40 – 500L, making it suitable for all kinds of fish and plant life. A high precision control system also allows more accurate adjustment of temperature and this model has a standard range of 20°C – 34°C.

    This makes it the perfect choice for fresh and marine water fish, and would be a welcome addition to the flora and fauna of any aquarium!


    • Explosion Proof: 2mm thickened quartz glass
    • Space saving and higher stability
    • Extra stick-on thermometer and sucker cup included
    • Suitable for both fresh and marine water


    • Weight: 358 g (200w)
    • Dimensions: 34.2 x 8.2 x 4.8 cm (200w)
    • Wattage: 100, 200, 300

    Interpet Deltatherm Aquarium Heater

    A heating system designed for tropical fish favourites, the Interpet Deltatherm is a double insulated and fully submersible model made with the highest quality components.

    Featuring a quick access, top view temperature control, it’s easier than ever to readjust your settings without ever having to remove your device from the tank, and a handy on/off light indicator system lets you know when your heater is in operation.

    The heater itself also has a fantastic temperature range of 16-34 degrees Celsius, meaning despite it’s target fishy demographic, it could also make a fine water warmer for marine and freshwater fish who prefer slightly cooler conditions to their tropical cousins.

    One downside of this system though is that to take truly accurate readings, it needs to be positioned at a diagonal angle, which can obviously be unsightly within your setup if aesthetics are important to you.

    Still, as long as you’ve got an Easter Island Head to hide it behind, it’s definitely a great option for all types of fish!


    • Designed for tropical aquariums
    • Also suitable for marine & freshwater fish
    • Double insulated and submersible
    • Provides range of 16-34°C


    • Weight: 231 g (100w)
    • Dimensions: 24 x 2.2 x 2.2 cm (100w)
    • Wattage: 25, 50, 100, 150, 200, 300

    Hidom Quartz Glass Submersible Fish Tank Heater

    Hidom’s HT range aquarium heaters have been designed and manufactured by industry veterans and this quartz thermostat heater is their latest in a long line of high quality products.

    If you’re someone who is quite obsessed with getting an even distribution of heat across the breadth of your tank, Hidom’s quite frankly bizarre range of available wattage options means you can get as specific as you want according to the size of your aquarium.

    And with those wattages including a pitiful 25w model and a conversely terrifying 500w version, Hidom is undoubtedly the best choice for very small fish tanks with very few pets inside as well as full scale mammoth ones with more visible fish than water.

    A temperature range of 20 – 34 degrees Celsius makes them a great choice for tropical, marine and freshwater fish and a 1.5mm thick glass structure ensures a quick and efficient heat transfer rate.

    Now that’s watt we call an aquarium heater!

    …We’ll see ourselves out.


    • Quartz Glass Thermostat Heater
    • 9 different wattages available!
    • Heat up to a 500L tank!


    • Weight: 295 g (500w)
    • Dimensions: 45.1 x 8.5 x 4.8 cm (500w)
    • Wattage: 25, 50, 75, 100, 150, 200, 250, 300, 500

    Hidom 50w Submersible Aquarium Fish Tank Shockproof Thermostat Heater

    This Thermostat Aquarium Heater from Hidom’s HT series offers high performance water warming for tanks of various sizes thanks to its range of wattage options.

    Utilising the latest in aquarium heating technology, this submersible device includes a simple set-up temperature scale that keeps your tank topped up with warmth and is perfectly suitable for both freshwater and marine tanks, with a temperature range of 16 to 32°C.

    Fantastic for keeping your fish den a visual delight to behold, the heater’s 1.5 metre mains cable means you’ll have plenty of room to manoeuvre when positioning the device within the aquarium, and heavy duty suckers also allow you to provide firm attachment to the side of the tank, keeping it well out of the way.

    Alternatively, if visuals aren’t a necessity, the cable also just offers you a great chance to position your probe in a spot which is going to give the most even spread of heat throughout, keeping all your fishes equally happy!

    For additional safety, it’s extra thick, heat and shock resistant glass structure ensure the core of the heater is also well covered, rendering it harmless should your fish come into contact with the device itself.

    Safe and secure, what more could you want?


    • Ideal for Tropical / Marine or Freshwater Fish
    • Range of 6 wattages for several tank sizes
    • Blast proof design


    • Weight: 191 g (50w)
    • Dimensions: 30.6 x 8.2 x 5 cm (50w)
    • Wattage: 50, 75, 100, 150, 200, 300

    Interpet Delta Mini Nano Aquarium Fish Tank Heater

    This is a slim and compact heater pad with a continuous heating output, which is great if your fish need the warmest possible water.

    It always heats to 5°C above ambient room temperature, and you’re pretty flexible in terms of placement. Pop it under the gravel, tuck it away behind the filter or just leave it on display if you aren’t concerned about the look for optimum results.

    An aquarium thermometer is included so you can monitor the water temperature continuously, and it is the ideal solution for small aquariums up to 20 Litres (4.4 gallons). There are two models available – this 15W, but also a smaller 7W which can cope with tanks up to 12L.


    • Two variations available
    • Low maintenance - just clean once per year


    • Weight: 240 g
    • Dimensions: 5.7 x 8.87 x 2.12 cm
    • Wattage: 15W

    Eheim Aquarium Thermostat Heater

    The EHEIM adjustable heater is an ultra-modern electronic thermal device that utilises the best available technology of today, while staying true to the classic hanging in the water rod design of old.

    Coming in a large range of different wattages, this simple enough looking design is actually constructed with a jacket material made from special laboratory glass, increasing the heating surface and serving as a kind of heat shield for the device. This ensures the optimum amount of heat is evenly dispersed around the tank, with larger wattages ensuring even the biggest tanks can be taken care of.

    A precise control dial at the top of the heater means changing the settings can be somewhat fiddly and of course, wet, however it can still conduct temperatures in an impressive range of 18 to 34 Degrees Celsius.

    So for those who like their heaters to be a quick and easy set-up, it’s a good choice for tropical fish.


    • Shock resistant shatterproof glass tube
    • Heating function indicated by on/off control light
    • Precise temperature dial
    • Temp range of 18 - 34°C


    • Weight: 449 g (300w)
    • Dimensions: 32.5 x 2.5 x 2.5 cm
    • Wattage: 25, 100, 125, 150, 200, 250, 300

    U-picks Aquarium Heater

    Suitable for 45-60L aquariums, this heater also comes in two other sizes as well so could even be appropriate for tanks up to 200L.

    The internal temperature probe is sensitive, so offers eact temperature control. It is in heat-resistant thickened glass and black quartz sand, making it explosion-proof and anti-corrosion. Perfect for saltwater and fresh water.

    When it is exposed to air or not in water, it will also turn itself off to prevent any dangerous accidents.


    • High precision temp control
    • Protection against explosions or damage
    • Doesn't look out of place


    • Weight: 340 g
    • Dimensions: ‎22.4 x 13.2 x 5.4 cm
    • Wattage: 100W
    • Hose Length: 6 inch hose

    Buying Guide

    Choosing The Right Aquarium Heater For Your Fish

    Keeping your aquarium in optimum condition for your fish is a lot more difficult than most people imagine and ensuring the water is constantly at a temperature they can thrive in can be a challenge without a good quality aquarium heater.

    Here’s some things you need to consider before making a purchase…

    Fish type

    The most important thing of all is to work out the temperature your fish needs to thrive, because if they require a constant source of high quality heat – you’re going to need a very high quality heater.

    Heater type

    Although we recommend the submersible heater, the most commonly used type of tank warmer, there are other versions which you may find more suitable for your needs. These are external, inline and substrate models.


    Rather than being labeled as different sizes, heaters are generally categorised by the amount of watts they give out. The bigger your tank, the more watts you need.

    Heater aesthetics

    The most popular kinds of heater are usually submersive, however some fish owners may be disappointed by the visual of a heater floating in their tank, which is what happens if you can’t get sucker cups to appropriately place your heater. You therefore might want to consider external or substrate heaters to not spoil the vision of your beautiful tank.

    Automatic turn off

    A great safety feature, this helps the tank stop from overheating by switching the heater off automatically when a desired temperature is reached, preventing it being heated constantly for long periods of time. Although not a necessity, it will certainly make your life easier.


    A thermostat is pretty much a must when it comes to aquarium heaters, as it makes the process of changing the temperature far less complicated. These can often come with readable LED screens which constantly update you on the current temperature of the tank, so you can always keep on top of what’s going on.

    Types of heater


    A heater which needs to be fully submerged into the water to work, they can usually be placed vertically or horizontally within the tank. Submersible heaters are so popular because they work in both freshwater and saltwater tanks and can also efficiently heat all different sizes of tank.


    External heaters are installed outside of the aquarium and often have a small hose as it’s heat source which hangs over the edge at the top of the tank. However due to this very reason they do not always distribute warmth so well. For small and medium sized tanks though they are a good option, as they don’t take up room in the small space you have.


    Inline heaters are similar to external ones except they need to be attached to the tank filter system, heating water as it is pumped back in. This can make them fiddly and complicated to set up. They also may need additional parts for them to work properly.


    If you’re looking for something a little more aesthetically pleasing, substrate heaters are often disguised as something like a rock, sea bedding or other sealife plant which can be heated via a cable hidden beneath the tank’s sandy base. However these aren’t particularly practical ways of heating an aquarium, and are quite rare.

    Other Buyers Ask...

    What is the ideal aquarium temperature for my fish?

    The standard water temperature for most common tank fish is 25 to 27 degrees Celsius, however it all varies depending on the type of fish you own.

    In general, you will be able to determine if your fish needs a heater or not based on whether it is a cold water or tropical fish.

    Cold water fish can function just fine at room temperature and so you may not even need a heater at all for them to feel comfortable whereas tropical fish are used to much warmer climates and so these scaled beauties require the standard 25 to 27 degree Celsius heat source.

    This is why you should never mix cold water and tropical fish in the same aquarium, as their needs are completely different!

    What power (watts) aquarium heater do I need?

    In product descriptions for tank heaters, you may have seen some wildly different promises of the size of tank certain wattages can efficiently heat.

    And while you’ll see some declaring they can power an 1000L tank, it’s unlikely they’d actually be able to evenly distribute heat across an aquarium of that size without some serious watts behind them (well over 500!).

    Below is a very rough guide of what size aquarium a heater will be able to sufficiently heat per wattage.

    As you can see this is not an exact science and so as long as you buy a wattage which seems to be able to cover the size you need, and you’re not wasting energy with an overly powerful heater, you should be fine:

    • 25 W is suitable for 4-30 L aquariums
    • 50 W is suitable for 23-45 L aquariums
    • 100 W is suitable for 45-90 L aquariums
    • 150 W is suitable for 68-135 L aquariums
    • 200 W is suitable for 90-180 L aquariums
    • 300 W is suitable for 135-275 L aquariums
    • 400 W is suitable for 180-400 L aquariums
    • 500 W is suitable for 200-568 L aquariums

    But if you have a particularly large tank, there’s no law that you have to go for big watts, and many fish owners instead opt to buy two heaters of sufficient wattage and then place them at opposite ends of the tank, ensuring evenly distributed heat.

    Another thing people tend to forget to take into account when choosing their power of heater is their own room temperature. If you live in a particularly cold area of the country, you may need a more powerful heater to sufficiently raise temperatures.

    How safe are aquarium heaters?

    People often worry about heaters because the idea of placing an electrical device into some water seems completely at odds with everything we know about electrical equipment.

    However what you have to remember is that these products have actually been designed for that very purpose and so are actually perfectly safe.

    Like with anything though, they can become dangerous overtime if they start to become faulty.

    So make sure you regularly check over your equipment to ensure they are no broken parts or frayed wires!