Aquarium Heater: 16 Things You Should Know (For Beginners)

Aquarium heaters are essential accessories for a tank that regulates the water temperature to be habitable for fish and plants.

So the question is, do fish and plants need a heater? Would tank inhabitants die without a heater? Is there a size limit to a heater and can it become too hot for a tank?

How Often Should I Replace An Aquarium Heater?

You should only change your aquarium heater once it’s not working anymore. Regularly check your heater and see if there’s any damage on it and if the heater’s function still works (which is to regulate water temperature), then there’s no need to replace it yet.

So what are the signs that your aquarium heater may not be working anymore? Before you do the steps below, you need to have a thermometer and a bucket of water at hand. The thermometer would be used to check the temperature of the (aquarium) water inside the bucket.

Once you’ve gathered those, refer to the common signs of a broken aquarium heater below:

  • Check the temperature of the tank. If the temperature of the tank is too hot or too cold, then that would be a sign that your aquarium heater is broken.
  • If the temperature of your tank frequently fluctuates then that’s also a sign that your aquarium heater is broken.
  • When the light on your heater is not responding that doesn’t automatically mean that the heater is broken. Certain types of heaters are “stealth heaters” which means you can’t see the LED light go on or off.
  • When checking the temperature of the tank by using either a thermometer or your own hands, make sure that the tank isn’t exposed to the sun and LED lights installed in the tank. This way, the temperature of the tank won’t be affected by external factors.
  • If there’s no water movement near the heater, then the heater is broken.

Once you’ve checked all the signs mentioned above and have confirmed that your aquarium heater is broken, then that’s the only time you’ll have to replace your heater. However, if your heater is working perfectly fine, then there’s no need to replace it every once in a while.

How Long Does An Aquarium Heater Take To Heat?

It would usually take 25-40 minutes for an aquarium heater to heat an aquarium. To completely warm up an aquarium, it would take 24 hours.

Then again, there would be several factors that would hinge on this timeframe such as tank size. Bigger tanks would need more time to warm up because there’s more water and the opposite happens for smaller tanks.

Another thing, the heater itself has to heat up before it can do its function of warming up the entire tank. With that being said, refer to the bullet list below to see how long a heater would heat up:

  • 40 minutes: 10-25 watt heater
  • 90 minutes: 25-75 watt heater
  • 120 minutes: 75-100 watt heater
  • 150 minutes: 125-140 watt heater
  • 180 minutes: 200-watt heater

As for tank capacity, refer to the bullet list below to find out how long a heater would warm up a tank:

  • 15 hours: 5-gallon tank
  • 24 hours: 10-gallon tank
  • 30-36 hours: 20-gallon tank
  • 48 hours: 30-gallon tank
  • 60 hours: 50-gallon tank

Can My Fish Survive Without A Heater?

No, any fish wouldn’t survive without a heater because fish need a consistent temperature in the tank to survive and live a healthy life.

With that being said, both tropical and saltwater fish need an aquarium heater to survive. Tropical fish need it because they require warmer temperatures to survive (75 to 80 degrees). Even if you’re a person who lives in a country that only has one season (tropical season), it still isn’t right to solely rely on that.

You’ll still need an aquarium heater to keep the temperature inside your tank consistent because there’s a big possibility for the temperature in your home to change once nighttime hits (hotter temperatures from morning until the afternoon and colder in the evening).

Also, it would be wise to have a chiller installed in your tank if the environment where the tank is set up gets too hot.

As for saltwater fish, they also need a heater because the temperature of saltwater is warm, therefore, marine life is used to warmer temperatures (75 to 82 degrees). The same logic for tropical fish applies to saltwater fish as well: if you live in a place where the tropical season is constant, then you’ll need to have both a chiller and a heater.

If fishes don’t receive their required temperature, they’ll eventually become stressed. Stress in fishes can lead to stunted growth, acquiring illnesses, and may even die.

Why Is My Fish Tank Heater Making Noise?

Your fish tank heater is making noise possibly due to how it’s positioned in the tank, the heating element is turned on, the suction cups are too close to the coils of the heater, and there’s too much moisture in the heater itself.

The aforementioned causes are the main reasons why your heater is making noise. Take note that some of these causes create a popping noise sound as well.

If you’ve noticed that your heater is making noise that doesn’t necessarily mean you should replace the entire thing. All you have to do is troubleshoot your heater and identify what causes the noise. The causes mentioned above have easy fixes so there’s no need to worry that much.

Why Is My Fish Tank Heater Flashing?

If your fish tank heater’s flashing or flickering then that means your tank’s temperature is fluctuating at a fast pace.

Once you see your fish tank heater flashing, there’s no need to panic since the issue would be pretty easy to fix. All you have to do is lower the temperature output.

Moreover, there are other reasons why your heater is flashing its lights such as the cycling process being too fast or there are electrical problems with the heater itself.

Can I Turn Off My Aquarium Heater?

Yes, you can turn off your aquarium heater but only when you’re going to do water changes. That’s because leaving it on all the time is safe, so long as it’s fully submerged in water.

You must turn off your aquarium heater when it’s out of the water because it can burn and crack if you leave it on.

Also, aquarium heaters aren’t going to break or overheat if you leave them on overnight or all the time since most heaters have an internal thermostat that will automatically stop the heater from warming up the tank once it reaches a certain temperature.

You also need to watch out for the water level inside your tank. If the water doesn’t keep your heater submerged anymore, then you must turn it off. Remember, aquarium heaters can’t be turned on when they’re not submerged in water.

Are Aquarium Heaters Hot To Touch?

No, aquarium heaters aren’t hot to touch. These heaters are designed to keep heat inside of the units so touching them shouldn’t burn you.

However, an aquarium heater can become too hot. According to Newcomb and Company, here are several causes of a heater becoming hotter than usual:

  • Sediment or buildup
  • Ventilation issue
  • Backdraft problem
  • Blocked flue
  • Missing inner or outer door for the pilot light

Why Do Fish Stay By The Heater?

Fishes stay by the heater because they prefer to be exposed to warmer temperatures. A lot of fish, both tropical and saltwater, prefer warm temperatures which is why they stay near aquarium heaters.

Observe your fish if they seem to always gravitate towards the aquarium heater because this would tell you that the temperature of your tank isn’t equal. What does this mean? Well, if you own a large tank, some areas may be a lot colder, especially areas that are farthest from the heater.

It’s best to have two heaters for larger tanks, this way, your fish won’t just stay in one area because two of your aquarium heaters would keep the water’s temperature consistent throughout the entire tank.

Is A Bigger Aquarium Heater Better?

No, a bigger aquarium heater doesn’t necessarily mean it’s better because it would all boil down to wattage, and small aquarium heaters are capable of providing the appropriate wattage that’s compatible with a certain tank size.

There’s been much debate when it comes to big aquarium heaters versus small ones regarding which is better to use in a tank. Some say that big heaters are better since they’re capable of warming up a tank a lot faster than small heaters do, while this may be true, this would only be good for large tanks.

Small tanks would most likely suffer from having a big heater whose wattage exceeds 50W. We’ll be providing a guide that would help you pick which heater is appropriate for your tank. This would show the compatibility of wattage to a certain tank size:

Tank GallonsWattage
5-10 Gallons50W
15-20 Gallons100W
24-40 Gallons150W
50-60 Gallons200W
75-100 Gallons250-300W

It’s best to stick to the guide shown above since this would greatly help you with choosing the appropriate heater for your tank. It would also lessen the likelihood of your fish getting cooked in the tank due to strong wattage. Of course, there are also a few downsides to having a small heater.

For instance, small heaters take longer to heat an entire tank and they struggle to keep the temperature inside a tank consistent due to not having a thermostat built in them.

It would be ideal to choose a heater that has a built-in thermostat so that it turns off automatically once the tank has reached the temperature it’s adjusted to.

Can an Aquarium Heater Be Too Big?

Yes, an aquarium heater can be too big. A big heater can go up to 100W and that would be too much for a small tank of 5-10 gallons.

Always refer to a guide to see which heater is compatible with a certain tank capacity. Why? Well, it wouldn’t be wise to get a big heater that has strong wattage and put it inside a smaller tank size because that would lead to several problems such as constant cycling.

Constant cycling would ensue with a small tank paired with a big heater because the small tank capacity will quickly heat up and cool down at the same time. Once that happens, it would eventually break your heater.

Is A 100-Watt Heater Too Much For A 10-Gallon Tank?

Yes, a 100-Watt heater is too much for a small 10-gallon tank. This wouldn’t be a good setup because it would cause the heater to cycle constantly and eventually end up breaking.

You don’t need a high-wattage heater for a small tank just to speed up the heating process. All you need to have is a heater that has a maximum of 50-Watts.

However, some aquarists argue that a 50-Watt heater may be too weak if you’re the type of person who lives in an environment that’s constantly cool in temperature. If this is the case, then try to get your hands on a 100-Watt heater. This would balance out the temperature inside the tank more efficiently.

Can You Put A 20-Gallon Heater In A 10 Gallon-Tank?

Yes, there are instances where you can put a 20-gallon heater in a 10-gallon tank. Such instances would be having your tank set up in a cold environment.

Having a heater that has weak wattage wouldn’t be sufficient even for a small tank, especially if the tank is in a cold environment (e.g. a room that has the air conditioning, winter seasons, etc.).

If this is the case, then you can certainly put a 20-gallon heater (100W) in a 10-gallon tank. Just be mindful that the heater must have a built-in thermostat to keep the temperature of the tank consistent.

Can I Use An Aquarium Heater For A Pond?

It’s not advisable to use an aquarium heater for a pond because heaters aren’t built to withstand the outdoor weather conditions, so you just might end up breaking the heater.

Instead of using aquarium heaters for your pond, it would be best to just go for a heater that’s meant for pond-use. There are lots of fish pond heaters in the market and these are meant to be used outdoors, so these won’t break if they’re exposed to cold air and such.

According to Everything Ponds, there are three types of pond heaters:

  • Gas-fired boilers
  • Pond De Icers
  • Inline electric water heaters

If you want to know more about these fish pond heaters, refer to this link.

Can An Aquarium Heater Be Too Powerful?

It’s possible for an aquarium heater to be too powerful. Most aquarists state that powerful heaters are most likely to malfunction, and once this happens, it would cook your fish and kill them.

While it’s okay to use a higher wattage for tanks that are located in cold environments, it’s still better to stick to the guide that we’ve provided.

However, if you still want to go for a powerful heater, then it would be best to choose a high-quality one that has a built-in thermostat as well. The best type of thermostats for a heater would be a digital thermostat and a mechanical/bi-metal thermostat.

The good thing about these thermostats is no matter how powerful your heater is, you have control over the temperature you want for your tank inhabitants.

Can You Bury An Aquarium Heater?

No, you can’t bury an aquarium heater, so you must avoid having the heater come in contact with gravel/substrate, let alone bury the heater in it.

Burying an aquarium heater would only cause trouble for you. Why? Well, most heaters are made out of glass and some are made out of impact-resistant materials (glass, polymer, resin, vented plastic), those heaters that are made out of  non-impact resistant glass would crack under the pressure of gravel.

Once the heater cracks, even just a bit, that would cause troubles for you. It wouldn’t hurt your fish because most fish tanks are non-conducting, however, if you reach in the tank and touch the water, there’s a possibility that you would get shocked.

Aquarium Heater

Cobalt Aquatics Flat Neo-Therm Heater, Fluval E-Series Heater, and Eheim Jager Aquarium Thermostat Heater are the best heaters you can get in the market.

The good thing about these heaters, apart from receiving high rates from aquarists that have bought it, these all come from reputable brands. That in itself guarantees that you’ll be getting your money’s worth for the quality you’ll be getting out of these heaters.

All three heaters that we’ve mentioned all have thermostats in them, so you wouldn’t have to worry about not having consistent temperature in the entire tank. Also, each heater has various wattages that would be appropriate for certain tank capacities (as indicated on their boxes).

Check them out here:

Cobalt Aquatics Flat Neo-Therm Heater

Fluval E-Series Heater

Eheim Jager Aquarium Thermostat Heater