betta tank heater

Betta Tank Heater: Guide on What to Buy

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Do betta fish need heaters? Yes, yes they do. Getting an aquarium heater for your betta fish sounds like a pretty straight forward issue to get past. That is until you see how many there are available in all of their various shapes, sizes and… wattages. If you are new to the world of aquarium heaters, your initial confidence can quickly go from 90 to nothing. But that’s what we’re here for!

Quick Summary: Best Betta Tank Heater

ViaAqua 50-Watt Quartz Glass Submersible Heater with Built-In ThermostatViaAqua 50 Watt Quartz Glass Submersible Heater
  • Built-In Thermostat
  • High Quality Quartz Glass
  • Fully-Submersible
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Elite Thermostatic Heater, 8-Inch/50-WattElite Thermostatic Heater
  • 50-Watt Aquarium Heater
  • Maintains Accurate Aquarium Temperature
  • Pilot On/Off Switch
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Aqueon Preset Aquarium Fish Tank Heater 100 WattsAqueon Preset Heater
  • Appropriate For Most Tropical Fish
  • Shatter-Resistant Construction
  • Automatic Safety Shut-Off Avoids Overheating And Damage
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AquaTop 200W Digital Heater with External ControlAquaTop Digital Heater
  • Digital Touch Control
  • Use In Fresh Or Saltwater
  • Heating Indicator Included
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Narrowing the Options

In days gone by, heating your aquarium meant purchasing one of only two available types of heating devices. That would be the one-setting-only, thermostatic submersible type. It was exclusively made out of glass. Or go for an automatic heater that you would hang on the back of the aquarium. Now, the assortment of available heaters for your tank can fill entire aisles of the pet stores. You can select from ranges of size and shape, temperature outputs, build-materials, wattages, control systems, and more.

Don’t get too discouraged or overwhelmed, though. It’s not too hard to make a smart decision on which heater to choose for your fish tank setup. I’d say that first and foremost, learning the following rule of thumb will help you get 90% of the way to finding your perfect aquarium heater.

You need at least 25 watts of power for every 10 degrees of existing ambient temperature per 10 gallons you need to heat.

For example, say the ambient temperature of your home is 70°F. You have a 10-gallon aquarium that you need to be heated to 78°F. For a single setting heater, you would need 25 watts of power to get that 8°F difference.

However, you could also get a 50-watt tank heater with variable temperature controls. If you think your home may be colder at other times of the year, that’s the way to go. That way, you could set that heater to the low side and have room to increase if necessary.

The Importance of Wattage

For many people, a fairly large concern is that their lack of knowledge and fear of hurting their fish. For the most part, aquarium heater issues arise when the heater being used isn’t the correct wattage for the capacity of the aquarium it’s being used in.

Remembering that rule of thumb above about tank heater wattages and aquarium capacities will help ensure that you end up with healthy and happy betta fish. Keep in mind that sales representatives may encourage you to get a higher wattage for the sake of making a higher sale. Always make sure to educate yourself before going into the pet store.

BettaSource’s Top Tank Heaters

ViaAqua 50 Watt Quartz Glass Submersible Heater

ViaAqua 50-Watt Quartz Glass Submersible Heater with Built-In Thermostat
  • High quality quartz glass
  • Fully-submersible
  • Visible temperature setting

This is a pre-set heater made of quartz glass, making it break-resistant. We like this one because it’s pretty easy to set up, using suction cups for secure attachment. The temperature setting is visible, and the device is fully submersible. The minimum 50-watt option might be a bit much for novice hobbyists with smaller tanks. But the construction and design is a good example of what you should be looking for with this type of heater, even if you need to downsize.

Elite Thermostatic Heater

Elite Thermostatic Heater, 8-Inch/50-Watt
  • 50-watt aquarium heater
  • Maintains accurate aquarium temperature
  • Pilot on/off switch

The Elite Thermostatic is a hang-on-the-back heater. This is a 50-watt product, but this brand does sell a “mini” 25-watt option. It’s not top-of-the-line by any means, but it’s pretty affordable and reliable. It’s a bit old-school (which isn’t a bad thing) and uses a pilot on/off switch and an adjustable dial to operate.

With this product, it’s important to remember that you must keep the heating element submerged (meaning you have to be a responsible fish owner and keep your water high). Take care to submerge the heating element first, let it sit, then slowly heat it up. You don’t want the glass to bust by plunging the already hot heater into cold water.

Aqueon Preset Heater

Aqueon Preset Aquarium Fish Tank Heater 100 Watts
  • Preset to 78°, accurate to +/- 1°
  • No adjustment required
  • Shatter resistant

This is a plastic/resin-covered preset heater. While it’s more durable in terms of drop-resistance, plastic and resin aren’t quite as good as their glass counterparts. However, they are cheaper, and this is no exception. This preset heater stays on at 78 degrees. It’s not particularly powerful but works fine as long as your ambient temperature is reasonable.

Essentially, this is a good, cheap placeholder until you can invest in something a little more substantial with a longer warranty (this one is just 1-year).

AquaTop Digital Heater

AquaTop 200W Digital Heater with External Control
  • Digital Touch Control
  • Temperatures adjustable between 20c-34c/68-93F. Heating Indicator Included
  • Suitable for tanks up to 50 Gallons

This is a digital heater, equipped with a dual temperature display. The temperature sensor is separate from the main device, making it more accurate and allowing for a more stable heat maintenance process. It is fully submersible, meaning you can tuck it away in various parts of the tank without a hitch. Additionally, this heater has memory storage, which is great if you frequently experience power outages. You won’t need to reset the temperature controls every time a strong wind blows.

Types of Tank Heaters

Preset Heaters

Preset aquarium heaters (also called Thermostatic heaters) are a type of aquarium heater that has an analog thermostat built into the device. Some types of preset heaters actually have a remote sensor that gauges the aquarium’s temperature separately from the main heating unit itself.

Nearly every thermostatic heater you can find is fully submersible. These submersible heaters all come with a line of some sort that indicates the minimum submersion depth needed to function without fail. In general, this is about an inch to an inch and a half from the top of the heater. In most cases, you will not have to or want to fully submerge your preset aquarium heater.

As was mentioned earlier, you really want to give these heaters a good 30 minutes of pre-soak time in the fish tank before you even plug them in. This will give the aquarium heating unit some time to acclimate its internal components to the existing temperature of the aquarium.

When you do go to plug-in and turn on the preset heater, you should really have a secondary thermometer on hand. Use this to verify the temperature.  Experience shows that it’s normal for preset heaters to be off by a few degrees right out of the box. If there’s a gap, keep it in mind when adjusting any settings. Also, note that it will likely grow larger over time as you near the time to replace the heater.

When mounting the preset heater to the betta’s aquarium you should preferably mount it vertically. If you read the manufacturer’s instructions (as you should), you will find these instructions, but some people still choose to mount theirs horizontally or diagonally. There is some worry about water breaching the seal at the top of the heater, causing failure and damages.

Plastic covered or resin heaters

Next is the plastic or resin-covered type of heater. You can consider this a closely related type of heater to the glass/quartz preset heater described above. Some refer to these heaters simply as “smart” heaters. They generally have a low-temperature variance and a built-in LED warning system. The warning system on these types of devices generally kicks in when the temperature of the tank is +/- 5°F from whatever temperature you set the device at.

Hang-on-the-Back Heaters

“Hang on the back” heaters are also known as “Automatic” and/or “Non-Preset” aquarium heaters. As the first of their many names implies, they are designed to “hang on the back” of the aquarium you are trying to heat. Their other common names (eg. “Automatic”) are a bit misleading though, as they do not adjust their power output by sensing the current temperature.

They work through what is known as a Remedial thermostat. When you make adjustments to the control dial on this type of heater, you would be either tightening or loosening metal contacts on a bi-metal lead. Essentially, this just means the heater is “on” for a longer or shorter amount of time. This also means you have to watch out for ambient temperature swings and season changes, adjusting accordingly.

If you have one of these types of heaters, it is more than important that you make sure that the water level is maintained at the required level indicated on the heater. Failure to maintain the proper water level will end up causing the heater to fail. Failure for these heaters generally means that the heater cracks under stress of dry heat. This is really not a good thing when you have it still plugged into an outlet and partially submerged still the aquarium.

On the plus side, they are almost always very affordable. Also, because they hang on the back of the tank, they will fit most any aquarium. Because of their affordability and easy use in virtually any tank, many people keep one or two of these heaters in a drawer to be used in case their primary aquarium heater fails.

Digital Heaters

These heaters are also closely related to the preset heaters as described above. They are actually almost completely the same in general except for the fancy digital temperature readout display built into them. Well, actually the temperature control circuitry is a bit more advanced than the typical preset heater provides.

Some of the reasons you may want to consider this type of heating system over the typical preset heater are:

  • They provide a dry detection auto-shutoff
  • Higher accuracy temperature control
  • Big and bright temperature display
  • 2x insulation surrounding the heating element

Under-Gravel Heaters

These types of aquarium heaters are really popular with new betta owners. These “under the gravel” tank heaters are made specifically with small capacity aquariums in mind. These mini heaters are supposedly heating rated up to about 5 gallons, but are really intended for a 1-2.5 gallon tank. That is to say, if you have an aquarium that is 5 gallons, you might be better off looking at a “real” in-tank heater like a preset or HOB heater.

They work on a sort of internal “automatic” setting that adjusts the temperature of the aquarium based on a hard-set internal temperature limit. Each device has its own temperature standards and variances, but as a standard, most will increase the temperature of an aquarium by around 5 degrees of the ambient temperature. Because most homes are heated to around 72°F, this 5-degree rise will get the temperature in the tank just close-ish to a betta’s preferred temperature.

What tends to attract people to these devices is that they are invisible except for their waterproof power cords. They are also always on, making them a “set-and-forget” type of heater. However, what you gain in convenience and aesthetics, you sacrifice in genuine quality.

There are a few reasons we haven’t recommended one of these in our buying guide. First and foremost,  you shouldn’t have your betta in a tank small enough for these to be a valid option for you. The only tanks these “under the gravel” options are good for are the 1-2 gallon tanks that misinformed sales reps will push on you. If your fish is in one of these tiny tanks, these heaters are better than nothing. That said, you should still invest in both a bigger tank and an appropriate heater.

In-Line Heaters

These types of heaters are can be nice to have in certain situations. Especially when you have a very large tank. Most betta fish owners, by a very large margin, will not have their bettas swimming in 50+ gallon tanks, so you can probably skip reading about these. I’m including their description in here anyway because this guide is about aquarium heaters, and this type is one.

These are a type of external aquarium heater that seems to be a work-around to the water circulation problem common to many fish tank heaters. In-line heaters heat the water outside of the tank first and then pass the heated water into the aquarium. In-lines seem to bounce back and forth in popularity over the past many years.

The most consistently popular type is the stand-alone inline heater such as the Hydor In-Line External Heater. That particular make and model of in-line heater has been around for quite a while and has gained a great reputation for working well and being reliable. Most people actually picture this particular heater in their mind when talking about inline heaters.

In general, I have not found in-line heaters of really any type to be particularly good at accurately and evenly distributing heat in the aquarium. Failure rates of the inline devices were always much higher than that of other forms of aquarium heaters as well. That being said, if you do find yourself fortunate enough to own a very large aquarium, and do not mind imperfect heating accuracy, these types of heaters are fairly bargain-priced as compared to buying multiple heaters that are submersible.

Things to Consider


When you do finally make your aquarium heating selection, you need to set it up in a way that there is good circulation around the heating element. Aside from safety concerns, providing a good amount of circulation around the aquarium heater will make it much easier to control the temperature. Good water circulation around the heater also makes the heater’s readings far more accurate.

Read the manufacturer’s directions thoroughly! (Yes, even if they are boring)

Bigger Tank Tips

One other thing to mention is that if you have a larger size aquarium and the temperature of your home is 25°+ degrees colder than you want your aquarium heated to, you can install a second heater following the same guidelines as stated above. For larger sized fish tanks, doubling up on your heaters rather than purchasing one very strong heater will let your aquarium distribute heat more efficiently.

Keep in mind that many heaters are specifically designed to heat only up to a certain temperature. If you try and heat above the recommended high-temperature setting, you may end up having to buy a new heater in short order. Heater failure, damage to the aquarium and injury to the fish may occur if you don’t carefully follow the guidelines for the specific heater you are using. Again, read the manufacturer’s boring directions thoroughly!

Extension Cords: Yea or Nay?

The power cords for aquarium heaters are specially designed and manufactured for use with a specific heater. Using an extension cord may not be the wisest idea. The power draw from the heater may cause inferior extension cords to heat up causing the cord’s insulation to fail. If you decide to go against this warning, at the very least, make sure that the extension cord is not coiled at any point. Coiling can increase the rate at which the extension cord heats up, and therefore increase the danger in its use. Please be careful with their use. If in doubt, don’t use them.

Also, most manufacturers warn against using power strips with your tank heaters. But if using one becomes absolutely necessary, make sure you are still following the U-shape rule.

Return Policies

You will probably not have to ever return an aquarium heater, but if you have to, you should take a look at the return policies on the particular make and model you decide to purchase. Some brands of aquarium heaters are actually pretty difficult to return.

When I speak about the return process as difficult, I am not saying that they can be impossible, but rather that they give specific instructions to return products directly to the manufacturer as opposed to the retail outlet that you purchased the device from. Maybe that isn’t a big deal to you, but I don’t like jumping through that hoop. As I said before though, you will most likely not have to return a heater because is defective out of the box.


Just in case you see this happening and start to worry after you set up a glass heater, it’s fairly common to have a small amount of condensation gathering on the inside of the heating enclosure. This is not necessarily a sign that your new quartz aquarium heater is leaking and defective. If you notice that the condensation is growing and pooling a good amount inside the bottom of the glass enclosure, you may have a problem. A little condensation on the inside of these glass heaters is a relatively normal occurrence though.

Basic aquarium heater setup

Acclimation and Submersion

First and foremost, when you go to install the new aquarium heater, you should place the device into the aquarium water at least a half-hour before plugging it in. Letting the heater soak in the fish tank while it’s un-powered will allow the device to acclimate all of its internal components to the initial temperature of the aquarium. By doing this, you are trying to avoid heater failure and damage.

With pre-set submersible heaters, you are going to want to make sure that you submerge the heater to at least the minimum water line. Aquarium heaters that are the “hang on the back” type should be submersed exactly to the water line indicated on the device.

You want to pay careful attention to the water level on these types of heaters because if the water line is either too high or too low, heater failure can occur. Generally speaking, it’s not hard at all to maintain the proper level of submersion with these types of heater. The water evaporation can cause the water line to lower over time, but you will be checking on your tank like a good betta owner… right?

Making and Checking Heat Adjustments

In general, you should not adjust the temperature on the heaters’ dial more than 5°F per day if your fish is in the tank. If the tank is empty, you can make larger adjustments.

When adjusting the temperature control dial on incremental (or manual) models, make the adjustments in small quarter-turns. If you can manage, smaller turns are better. Automatic heaters do not, of course, have the ability to adjust the temperature setting like this.

Specifically, with the pre-set heaters, you should do a few water temperature tests. It’s pretty common to have the real temperature of the tank be off by a few degrees Fahrenheit with pre-sets. You could have your pre-set tank heater at 78° and come to find out much later on that the real temperature in the tank is 75°. While this doesn’t sound like too big of a difference in temperature, to a betta fish, it is.

With Multiple Heaters

If you are one of those people with a lucky betta fish swimming in a large tank and are subsequently using more than one heater, we recommend adjusting one heater at a time before trying to use both at the same time. It can sometimes be difficult to set the correct temperature for an individual heater while there is another heater currently running in the tank.

That advice does kind of go out the window if you are running two heaters because the combined wattage is what you need to properly heat your aquarium. In that case, you are going to have to try and set both at the same time, making micro-adjustments to both to get that perfect temperature. This can take some time as you will be in a sort of temperature war with the heater you are not fidgeting with.

Not to mention that heaters are often off by a few degrees, so using their temperature reading gets confusing. Just be patient and have a thermometer or other temperature reading device on hand.

Water and Electricity Safety

Please make sure that you employ a drip-catch when connecting the heater to a power supply. This is not a difficult thing to do and doesn’t cost anything. Imagine a stream of water traveling down the heater’s power cord to the power outlet.

If the cord is running in a straight line at a downward angle to the outlet, water will enter the outlet. You do not want this. To stop this from happening, make sure that there is enough slack in the heater’s power cord to fall just below the power outlet, and then rise up again to attach to the outlet. Imagine a U-shaped bend in the power cord that falls below the power outlet.

This U-shaped bend in the power cord will be the lowest point that the water can travel down the cord. As water cannot travel on its own at an upward angle, the U-shape will keep any water traveling down the power cord from entering the power outlet.

Changing Your Water

When it’s time to change out the water in the betta tank, you should remember to turn off any heater as well. You really don’t want to expose the heating element or the heat sensor to air. This may not break the unit all at once if you do by mistake, but it will shorten the life of the heater. It’s also a good idea to let the heater sit while turned off and still submerged in water for around 20 minutes before the actual water change. This will give the heater some time to cool off and let the temperatures of both the water in the tank and the heater equalize.


All in all, you need to take into consideration only a few different things before making that final decision.

  • The size of your tank
  • The fish you choose to keep
  • Regular outside temperature fluctuations
  • Temperature sensitivity
  • Your budget

In most cases, choosing a typical preset heater for a 10-gallon tank will suit your betta just fine. Taking a look at the under-the-gravel heating options would be wise for tanks in the 2.5-gallon range. You probably want to veer away from those in-line heating options unless you have a very large tank. Don’t forget to re-read that handy Rule Of Thumb about choosing the correct wattage. That’s near the beginning of this article.

Whatever heater you end up with, don’t forget that you’re shooting for that 78°F-80°F range. And lastly, you might consider picking up one of those Hang-On-The-Back heaters. It may come in handy as a backup, should something go wrong unexpectedly.

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