Freshwater Fish

The Best Tank Heater for Betta Fish

Aside from selecting your aquarium, the most important part of setting up a betta tank is choosing your heater. Like most tropical fish, bettas require consistent, warm water temperatures to stay healthy and thrive. Choosing the best betta heater for your tank, whether it’s 5 gallons or larger, is a critical part of the process.

Some aquarium kits come with a heater, but more often than not aquarists have to add one to their setups. With so many options, how do you choose the best type of heater for your betta tank?



You need an aquarium heater for your betta setup because they prefer warm aquarium water. The ideal range for bettas is 75°F to 86°F. Your tank is unlikely to stay in this range naturally without using additional heat.

Bettas also do not do well if the water temperature fluctuates more than a degree or two. Frequent changes in temperature can make your betta fish feel stressed and sick.The most common reason a betta fish loses color or stops eating is a tank that is too cold or changes temperature too much.


A good heater with a built-in thermostat will keep your tank at the set temperature automatically. You can monitor the temperature with a thermometer sticker on the side of the glass or with a thermometer in the tank. Your temperature may vary by a few degrees depending on the location of your thermometer and heater.

Do you still need a heater and temperature gauge for a betta tank? Yes! If you can’t find a heater that will fit in your tank, it’s probably too small for your fish. Upgrade to at least a 5-gallon setup with a heater and thermometer, and your betta will probably be a lot happier.


There is actually a wide variety of heaters on the market for aquariums and terrariums. Most of these styles are not suitable for small fish tanks or betta bowls. Briefly, the types of heaters you’ll encounter while shopping include:

heater style How does it work best heater for
Submersible and submersible heaters Sits partially or fully submerged in the aquarium. When the water temperature drops below the desired setting, the thermostat turns on the heater until the temperature rises enough. Aquariums of all sizes
sump heater It fits inside the filtration system and heats the water as it flows into the tank or pond. Large aquariums (over 100 gallons) or ponds with extensive filtration systems.
under gravel heater The heating cable is sandwiched between the substrate layers of the aquarium and the heat is concentrated at the bottom of the aquarium. Not a popular method in aquariums since the mid-1990s. Primarily used in large aquariums (over 50 gallons) with an emphasis on keeping live plants rather than fish.
Thermal mate under the tank The heating pad is placed under the aquarium and heats the bottom of the tank. Glass terrariums and reptile tanks


The best styles of heaters for tanks under 50 gallons and smaller fish tanks are submersible and submersible types. Both styles typically have a glass tube containing a heating element and thermostat that is placed inside your aquarium.

When the thermostat turns on, the inner element heats up and heats the water around the glass tube. Thermometer settings are adjusted using a dial or control knob.

The main difference between these styles is that a submersible heater is not completely waterproof. Instead, the control mechanism sits out of the water, and the heater attaches to the top edge of your tank, similar to a HOB filter. Submersible heaters are completely waterproof and sit completely underwater in your aquarium.


Submersible and submersible heaters can be set by moving their control dial or knob and selecting the desired temperature. Depending on the conditions in and around your tank, you may need to make further adjustments. In the summer, for example, I have to turn up the heaters in my aquarium a bit to compensate for the air conditioning.

Submersible heaters can be easier to adjust because their control dials sit outside of the aquarium water. Rather, you may have to reach into your tank to adjust your submersible heater. But submersible heaters are usually higher quality and last longer. They are also usually more expensive.


Heaters are rated by how much energy they use per hour, in watts. The right heater for your tank will depend on how much water it holds and how much you need to raise the water temperature. If your home is on the warmer side year-round, you can get by with a heater that uses less energy and has a lower wattage.

However, if you need to raise your aquarium more than 10 degrees above ambient temperature, you may need a heater with more power. You can choose the next size up, but you will need to monitor the temperature of your tank during the warmer months. Otherwise you could overheat your tank.

I don’t recommend using tanks under 5 gallons for bettas, and heaters under 25 watts are often unreliable. Here are some guidelines to follow when selecting a heater for your tank:

Aquarium size (gallons) Lifting water ~10°F Raise water above 10°F
fish tanks and bowls 2.5 and under (not recommended for bettas) 5 to 7.5 wattsMay not be reliable 7.5 to 10 watts May not be reliable
5 15 to 25 watts 50 watts
10 50 watts 100 watts
20 to 25 100 to 150 watts 150-200 watts


Heaters can pose a safety risk, so care should always be taken when handling or using them. I was about to start a house fire when water from a plastic container evaporated under the glass tube of the heater. The heater was plugged in so when the thermostat turned it on the glass shattered and started melting the plastic container.

If you have to remove the heater from your tank, always unplug it and let it cool down first. Keep your heater anchored to your tank properly so it doesn’t move. The glass tube is fragile and can easily break or crack if it hits the side of your tank or collides with your décor.

If your heater’s glass tube breaks or shatters while inside your tank, immediately unplug the heater!Do not reach into the tank while the damaged heater is plugged in, or you may be electrocuted. This is a rare event. I have only had this problem once in 35 years of fish farming. Leg warmers are generally safe if used as directed.


Let’s take a look at a selection of popular aquarium heaters and compare the ideal tank sizes and temperature ranges. While premium heaters can cost up to twice as much as less expensive versions, they are generally more reliable, durable, and long-lasting.

I have several high-quality submersible heaters in my collection that are over 25 years old and still work perfectly. Therefore, you can think of a heater as a long-term investment. If you go for a cheap heater, it may not be as reliable and you may need to replace it more often. For a small betta tank heater, this may not be a problem.


  • Heater Type: Submersible
  • Thermostat: Yes, integrated
  • Power: 25 and 50 watt versions
  • Temperature Range: Adjustable from 66°F to 96°F
  • Size: 3.2 x 2.2 x 7.8 inches
  • Ideal Tank Size: 25W: 5 Gallons; 50W: 10 gallons

If you want to avoid the more finicky aquarium heaters, this «unbreakable» design from Cobalt Aquatics might be the one for you. Instead of glass, the heater tube is made of a durable thermoplastic resin. This heater can take a hit and still work! I think this is the best betta fish water heater in this review.

The Cobalt submersible has a built-in thermostat with an adjustable temperature range, offering a lot of flexibility in its use. The heater comes with a cover that sucks into the side of your tank. The flat heater is just over 2 inches thick and can change its orientation on the sleeve to make the display easier to read.

The Cobalt comes in a wide variety of sizes suitable for tanks of all sizes. The 25 and 50 watt models are ideal for 5 and 10 gallon betta tanks. It’s easy to set with the touch of a button and will automatically shut off if the temperature exceeds 96°F. The display indicates both your set temperature and the actual temperature in your tank.


  • The thermoplastic housing is unbreakable and won’t crack or break like glass heaters do.
  • Easy to adjust settings inside your tank with the one touch control button.
  • The display shows both the temperature set on the heater and the actual temperature inside the tank.


  • The flat design isn’t much narrower than a standard glass heater and doesn’t really save much space in the tank.
  • The expensive and over priced heater may exceed the budget of some users.
  • The heater does not appear to be as durable as traditional designs and may need to be replaced after a couple of years of continuous use.


  • Heater Type: Submersible
  • Thermostat: Integrated
  • Power: 50 Watts
  • Temperature Range: 78°F
  • Size: 5.2 x 1.6 x 3.5 inches
  • Ideal tank size: 10 gallons

If you’re looking for a bargain, you probably can’t find a better option than the Tetra HT 50 Watt Submersible Heater with a built-in electronic thermostat. This little heater has a durable cap to protect the glass tube from damage. It is the ideal size for a 10 gallon betta tank.

The Tetra keeps things simple and I think that’s its most notable feature. Instead of fumbling underwater to adjust the temperature, the Tetra’s thermostat automatically heats your tank to 78°F. The red light tells you when it’s heating up, and the green light comes on when it stops.

If you need a lot of flexibility in a heater, this may not be for you. But if you just need a reliable betta tank heater with a thermostat, this is a great option. I keep an older version of this heater on hand for emergencies, and it never lets me down. It may not be as complete as other heaters, but for the price it’s hard to beat!


  • Inexpensive submersible heater with a thermostat that should fit most betta keeper budgets.
  • Red and green lights tell you when the heater is on and when your tank has reached the set temperature.
  • The built-in thermostat automatically heats your tank to 78°F, so you don’t have to adjust your settings.


  • The temperature is not adjustable, so if you prefer a temperature other than 78°F, this heater will not work.
  • May not work well for tanks located in cooler areas as the heat level cannot be increased.
  • May be too powerful for smaller tanks and betta bowls.


  • Heater Type: Submersible
  • Thermostat: integrated in an external controller
  • Power: 300 watts
  • Temperature Range: 61°F to 90°F
  • Size: 7.5 inch long heater rod
  • Ideal tank size: 30 to 60 gallons

While most betta tanks are 10 gallons or less, you can certainly keep a male or a group of female bettas in a larger tank. This fast-heating 300-watt submersible heater from Hygger is ideal for 30- to 60-gallon tanks and is packed with useful features.

The Hygger 300 is a more complex setup than the other one-piece heaters on my list. The glass heating rod is housed in a protected thermoplastic case that attaches to the side of your aquarium. It connects to the external control panel, where the digital display is easy to read and adjust.

The digital display and external control panel is what really makes the Hygger stand out from the other heaters on the list. Since it is not underwater, the screen is very easy to control and adjust. The wide temperature range and overall design offer plenty of flexibility for setting up larger tanks and community tanks.


  • The largest heater on the list and suitable for 30 to 60 gallon tanks (500 watt model is also available for 60 to 120 gallon tanks).
  • Quickly and quickly heat the aquarium water to adjust the temperature.
  • The external display panel is easy to see and can be adjusted with the push of a button.


  • More complicated to set up and operate than one-piece heaters and requires all three parts (heating rod, control panel, and power cord) to work.
  • Not suitable for smaller tanks under 30 gallons or betta bowls.
  • The premium price tag may be too expensive for some fish keepers.


  • Heater Type: Submersible
  • Thermostat: Integrated
  • Power: 25 Watt
  • Temperature Range: Varies
  • Size: 6 inch long heater rod
  • Ideal tank size: 5.5 gallon tanks and bowls

If you need a small betta tank heater, consider this mini option from Fluval. It is the ideal size for small 5 gallon aquariums and straight sided fish tanks. The fluval isn’t fancy or packed with features, but it’s a reliable and incredibly affordable little heater. It would also be an excellent choice for a breeding or quarantine tank.

The fluval Marina is an old school glass tube heater that has been on the market for years. The built-in thermostat does the hard work of turning the heater on and off for you. You can adjust the temperature by turning the control dial up or down. It couldn’t be easier to use!

The fluval can be a bit trickier to set up than other designs because the dial is underwater and the screen doesn’t list temperatures. You need to turn it on first and see how hot your aquarium gets, and then adjust the temperature up or down from there. Still, this is a great option for small tanks or larger betta bowls.


  • The inexpensive, old-school design is a reliable classic.
  • It has an integrated thermostat and a protective cap on the glass heating tube.
  • The small 6 inch long heating rod should fit inside most 5 gallon tanks and fish tanks.


  • The temperature dial is not marked, so you will need to allow the heater to come up to temperature before you can adjust it up or down.
  • The temperature dial is underwater when in use, so you need to reach into the aquarium to adjust it.
  • Limited use and flexibility as your maximum tank size is 5.5 gallons.


  • Heater Type: Submersible
  • Thermostat: Integrated
  • Power: 50 Watts
  • Temperature Range: 63°F to 94°F
  • Size: 2.7 x 1.4 x 4.5 inches
  • Ideal tank size: up to 6 gallons

What do you do if your tank is curved and you can’t fit anything next to it, or if you need a heater for a betta tank? One option is this fascinating mini heater from Hygger. Instead of using a long glass heating rod, this heater is flat and housed in a thermoplastic housing.

The Hygger Mini sits at the bottom of your tank or hangs in an inconspicuous corner if you prefer. Its nearly indestructible design is durable and protects your fish from harm. The external control panel makes it easy to adjust without having to get your hands wet as well.

The Mini’s heating unit has an LED display that shows the current water temperature and has a light to indicate when the heater is on. The built-in thermostat takes care of the hard work, so you can sit back and enjoy watching your betta play. This is an ideal option for oddly shaped tanks and bowls under 6 gallons in size.


  • The unbreakable flat casing makes the heater almost indestructible.
  • External control panel and 1-touch button make setup and adjustment easy.
  • It does not need to be anchored to the side of a tank, making it ideal for curved tanks and betta bowls.


  • More expensive than the other options for small tanks and betta bowls.
  • It can be too powerful and will overheat tanks less than 5 gallons in size.
  • To lower the temperature setting, you must reset the control panel and adjust the temperature up to the desired number.


There are many options when looking for heaters for your betta fish. While you can always go for an aquarium kit (buy a betta fish tank with a heater), adding a heater is usually not an expensive proposition. It is definitely worth investing in a betta tank heater with a thermostat if you have that option in your price range.

The good news is that most designs these days include a thermostat, even on budget or inexpensive heaters. Choosing between aquarium heaters likely comes down to your price range and the list of features you need for your tank. Even betta tank heaters come with premium features these days!

Hopefully you’ve found a couple of suitable options for your tank on my list, and we’d love to hear which heater you pick in the comments! If you still need help deciding, consider these factors:

  • If you’re looking for a premium heater that’s unbreakable and comes in a wide variety of sizes, my top high-end pick, the Cobalt Aquatics, is a great option.
  • For aquariums larger than 30 gallons, look to the best option for larger tanks, the Hygger 300.
  • If you need a heater for a small tank or betta bowl, consider:
    • Marina fluval for 5 gallon tanks.
    • Hygger Mini for bowls and tanks 6 gallons or less.
  • For fish keepers on a budget, the Tetra HT gets the job done and is a dependable, long-lasting workhorse.

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