Tank Maintenance

How To Keep Your Fish Tank Warm In A Cold Room? Save Your Fish!

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During cold days, your room probably has a low temperature. As a result, your fish might need a warmer environment to continue to thrive. At this point, you need to keep your fish tank warm by installing a heater.

You might have a lot of puzzles about how to keep your fish tank warm. Right? The first thing to do is to get a heater but there are some short-term solutions like using a blanket and a wax candle that can help you keep your fish tank warm!

Struggling with all the questions such as what to do when the room is always cold or how do to deal when there is a power cut and so on? Do not worry, you will get all solutions to your question in every sentence you read in this article.

Here I will be explaining the ideal temperature for your fish. Besides, what to do in different scenarios with the motive to keep your tank warm. The only thing, for now, you can thoroughly go through this article to ease your questions and worries.

Why Do You Have To Keep Your Fish Tank Warm?

Temperature is a prominent factor for a fish to survive. Therefore you need to be very aware of the relation between fish and temperature. It is the water temperature that allows fish to thrive and survive accordingly in a fish tank.

The fish body adjusts to the temperature of the water. Hence, they are immensely affected by the alteration of the water. The water temperature can change all aspects of fish survival in the fish tank.

For Breathing

Fish breathe by the flow of water into the mouth and forcing it out through its gills. Through these pathways, your fish intake oxygen in a fish tank. However, as the temperature alters, the oxygen level in water decreases or may not be enough for your fish.

If the water temperature becomes critical, the fish cannot breathe well. Therefore, it is necessary to maintain a warm fish tank with a standard level of temperature before it is critical.

For Reproduction

When you have to breed your fish, temperature plays a vital role. It may not be an issue with cold water fish if the environment is already cold. However, you must maintain the standard level of temperature.

For further information, check Easiest Fish to Breed in Home Aquarium to Make Profit and Top 8 Easy To Care Cold Water Aquarium Fish

Besides, warmer water fish prefer a higher temperature. So, you must maintain well to avoid a decrease in the number of fish in the fish tank.

For Proper Digestion And Feedings

Your fish’s metabolism is also affected by the water temperature. When your fish in the water at optimum temperature, they will function well. Hence, your fish will like to be fed well.

Please check about feeding fish in my two articles for detailed information:


As we are aware that fish are very affected by temperature, water with minimum temperature can be lethal to any fish. Alteration of temperature causes algae growth, change in water oxygenation level, and impacting fish’s metabolism. Hence, it could lead your fish to death.

To avoid such algae growth, you can put Best Algae Eaters For Freshwater Aquarium and use a natural way to remove algae in your aquarium.

Temperature In The Wild V/S In Your Tank

Every fish has a standard temperature range where you would see them thrive. From range, I mean that fish do not need exact temperature.

In the wild, you will not see a heater for ensuring the temperature. Hot summer, rain and winter nights all work to ensure that fish of the natural environment do not experience the same temperatures for too long.

The temperature of water in the sea and ocean does not change quickly as it takes a day or even a season to complete. On the other hand, you would find that even a small amount of water can quickly heat up or cool down. And yes this would cause problems!

So, you must maintain the temperature.

What Is The Recommended Water Temperature In Fish Tank?

Here is where things get a bit puzzling.

Just because your fish is alive, does not mean it is thriving well.

Every fish has its standard temperature range and tolerance level to the alteration of temperature. When it comes to the matter of preference of temperature, fish will be categorized as below.

Fish Type Temperature Range
Tropical fish 75 F to 80 F or 24 C to 27 C
Coldwater fish Below 68 F or 20 C
Temperate fish Wider range, often overlapping the above.

You would find the fish that come from large bodies of water, like the ocean sea and big lakes, are less able to adjust the alteration. Due to their stable large ecosystem temperature, the fish cannot adapt to the fluctuation in the fish tank.

Temperate fish are those which do not fall in the cold or tropical category. Yet they also have a preferred temperature range for their optimum health.

Related articles about diseases:

Preparation For Colder Room

As the season changes, your room temperature may also be changing. And, winter not only bothers you but also your fish. Therefore, you might be wondering what to do to come up with a solution.

Here, I will be writing all the scenario solutions that you could consider.

Make sure your fish tank heater is in proper condition:

Check Your Heater Size

You could get a good fish tank heater as per rule is 5 watts per gallon of 55 gallons or a smaller aquarium. Moreover, you can consider additional 3 watts per gallon for over 60 gallons. Always use a larger size or second heater for a colder room.

Here is the heater guideline based on the standard room temperature of 68 F to 72 F.

To Increase Above Room Temperature
Aquarium Size 5 F 10 F 15 F
5 Gallon  50 watt Approx. 50 Watt 50 watt
10 Gallon Approx. 50 Watt  50 watt 100 watt
20 Gallon 50 watt 100 watt 100 watt
30 Gallon 100 watt 100 watt 150 watt
55 Gallon 150 watt 150 watt 200 watt
75 Gallon 200 watt 200 watt 300 watt
90 Gallon 300 watt  Approx. 300 Watt 300 watt

Check The Condition Of Your Aquarium Thermometer, Are There Any Damage?

Before removing the heater from the aquarium let it cool for at least 30 minutes after you unplug it. Also, replace the heater if you see any damages or wear visible.

Then remove algae build-up or mineral deposits to reduce the risk of overheating and to improve performance. And, wait for 30 minutes after you put back your heater in the aquarium.

Check The Indicator Light

If you have an adjustable feature heater, make sure that the indicator light is working. If the light is off, rotate the control dial slowly until the indicator is working and check if the heater tube is generating heat.

Once you are satisfied, reset the dial to the desired temperature level.

And, if you have an Aqueon Branded heater, then keep in mind that the Aquatic falt heater and Mini Heater do not have an indicator light. However, Aqueon Preset Heater will indicate light only when it is heating the water.

Consider The Right Placement For Heater Inside The Fish Tank

Placing your heater in the right place is something you should take proper care of. Therefore, heaters should be near the filter or circulation pump to ensure even heat distribution.

You can install a submersible aquarium heater horizontally near the bottom of the tank for best results. Also, it can be placed vertically as per your preference. Moreover, you should not keep decoration near the heater to avoid uneven distribution of heat.

Know The Right Way To Make Temperature Adjustments In Fish Tank

Since your room is already a cold place, it would be better if you find a place for an aquarium where it is warmer. If that is not possible then you would want an additional heater.

If you are making adjustments to your heater, allow at least a few hours before checking the results. Hence, try not to change your aquarium’s water temperature suddenly as this might stress the fish.

What Happens If the Aquarium Temperature Is Too Low?

Low temperature can also cause a problem for tropical fish. It not only affects fish environments but also affects almost every survival stage of the fish. Hence, your fish will become slow and sluggish and some may die if not taken care of before it is too late.

It is similar to the condition that a person is not able to be comfortable and might catch a cold without clothes or bedding.

How Do You Maintain The Ideal Temperature In An Aquarium?

It is not enough to just get the actual range of temperature for the fish. You will have to also maintain the ideal temperature.

If you could find the inside temperature of the aquarium then you have won half of the battle. Unfortunately, cold water and warm water look the same. Therefore, you should get an accurate thermometer.

And now when you have a thermometer it is time to take a closer look to maintain temperature.

Getting The Basics Right

Start with placing your tank in the right place. An open window or AC vents will affect the temperature in your aquarium.

And yes, just because it is colder does not make sense that you should directly place it in the sun. This can cause the water temperature to soar. Hence, it is important to set the aquarium at the right place.

Can I Keep An Aquarium On Balcony: Is It Really Possible? Check out the answer here. You may also get some idea on the Most Common Beginner Aquarium Mistakes to avoid any in the process.

Heating Your Aquarium

Is it really cold? Time to use your heater!

All you can simply do is turn on the aquarium heater. This handy little device under your water will continue to warm your water until your desired temperature.

Maintaining The Temperature Automatically

Wouldn’t you want something that you could just set up your heating and cooling equipment to remain switched off and only turn on when required?

The exact product you desired will be an aquarium heater controller.

Just plug your heater, set the desired temperature, and walk away. Hence, your heater will automatically turn on if the water temperature drops below your setting.

Similarly, your heater will turn off and the fan will turn on if the temperature increases.

Therefore, you would not want to miss the purchase list after knowing that. Right?

How To Keep Fish Tank Warm If You Have Issue Of Heater?

Having an aquarium heater available all the time without an issue is not possible due to which your fish might suffer no matter what season it is!

Check out the following guides that will save your day when there is a power cut, aquarium heater breakage, and you are not prepared with a heater.

What To Do If Your Heater Is Out Of Service

You would someday face problems due to the heater not working. So, wondering what to do at the time. Just keep reading further below.


You would require the following if your heater is out of service.

  • A bucket of water and a thermometer
  • Thick towel or blanket, newspaper
  • Other types of heater.

Step 1: Check The Heater Status

Check the light of the fish tank if the heater is on or not. Simultaneously, use a thermometer to find out the temperature of the water.

Also, check the heater malfunction by turning it on while placing it in a bucket of water and check the temperature.

Step 2: Fix The Problem If Heater Is Not Truly Broken

Once you check the heater, if it is working, place it in the right place as per the heater type.  Therefore, attach at the top of the fish tank if your heater is an immersion heater. Also, you can change the battery in the case of a battery-powered heater.

If it is not broken, bring a repairer instead of fixing yourself or you can a new one if needed.

Step 3: Retain The Existing Heat In Fish Tank

Paper is an insulation material. Therefore, you can use newspaper to cover your tank to retain heat for a longer time. However, if you do not have enough newspaper then covering with a blanket would be fine.

Moreover, aquarium light can also help to retain heat in the fish tank. Turning on light and covering the hood would make it easier to catch fire. Therefore, do not cover it and remember it is just a temporary solution.

Step 4: Use Other Heater

If you are lucky enough to still have power, then turn on other types of heaters in your house. Place the heater next to the tank. This can increase the temperature of the room to keep the tank warmer in winter. But, keep in mind to frequently check up on the temperature to be maintained for your fish safety.

But, you might be wondering what if you do not have a heater and how to heat the tank faster. You just have to follow the combined steps of the third and fourth steps. However, you will require a heater as per your tank as soon as possible to maintain the temperature.

What To Do If There Is A Power Outage?

Everyone is not lucky to have power 24 hours a day. Right? Do not worry I have a solution for that case as well. Also, some of us have a long time power cut. What to do in such cases? Find out here.


You would require the following for your tank temperature maintenance.

You can use Candle by the Hour 48-Hour Horizontal Candle, Eco-friendly Natural Beeswax with Cotton Wick.

Similarly for jars, Ball Regular Mouth 32-Ounces Mason Jar with Lids and Bands (2-Units), Pack Of 2, Clear is the best. These small jars are at an affordable price and guess what! You can use them later for storing and decorations.

  • Materials for floating water container as well.

Step 1: Retain Heat

The first step you need to do is to cover the fish tank with a thick blanket or towel. However, newspapers can also be used to cover the tank to retain the tank.

Step 2: Make Water Containers

Most of us think of adding warm water into the tank when the heater is not available. And yes that can be done but not directly. You should use a water container.

  • Boil some water and pour it into the sturdy plastic container that has a tight seal.
  • Also, make sure the hot water does not melt the container.
  • Also, add some dechlorinating fluid inside the container to prevent it from leaking.
  • In case you have a larger tank, use more such containers.
  • The water level rises when you place the container. So, remove some water before placing it in it.
  • Replace or refill a new one when the temperature drops down.

Step 3: Make An Emergency Heater

  • Firstly, melt the candle wax and pour it into the jar which is filled with sand and wick on top of the sand.
  • Secondly, once the wax cools down and turns hard, put it in the tank to raise the heat up.
  • Then, you can use tin foil to cover the surface aquarium, make the hole fitting emergency heater to protect fire, and keep the tank warmer.
  • You can make an extender or can support the heater in a higher tank.

Just in case you want to heat up quicker without power, choose second, third, or both.

What To Do When You Do Not Have Any Heater

If you do not have any heater then you can use the above steps or the guide that I have mentioned below.


Step One: Turn Up The Air Pump

You can start by connecting and turning on the battery-powered air pump. The air pump allows much oxygen flow in the water. Therefore, you should pack air- pump power outside the Mylar emergency blanket.

These devices usually work for about 8 to 16 hours on a set of batteries.

However, bubbles are not much used in saltwater because of the water movement and loudness while in operation.

Step Two: Arrange The Heat Packs

Four to six good supplies of emergency heat packs with 60- hour warmer to 72 – hour warmer would help to warm the tank. Therefore, you can evenly space the heat packs around the tank attaching them with sticky duct tape.

A good rule of thumb is to install 2 heat packs per 25 gallons of the tank at a time. Therefore, for your 75-gallon tank, you can use 6 warming packs.

Step Three: Wrap The Tank In An E-blanket

Now, you need to wrap the mylar emergency blanket around the tank. Also, make sure there is a bit of looseness around the heat packs.

Also, tape the blanket like a tent at the top and make sure the power pack and air pump are not inside the mylar emergency blanket.

And yes more heat packs and more batteries will keep the tank warm and aerated for a longer time.

Frequently Asked Questions

Which Are The Best Aquarium Heaters That You Can Get For Your Fish Tank?

You would find many brands selling aquariums or fish tanks. However, there are a few best options I can suggest to you.

Aqueon Submersible aquarium heater is best as it is shatterproof and the light feature allows you to know the heater status and keep your tank warm.

Marina Aquarium Heater is an effortless one you can get to heat up.

Tetra HT Submersible aquarium heater is another that is affordable to many people. Moreover, this heater has enough essential functions that you can place anywhere.

Also, the Fluval Aquarium heater and Top Fin Aquarium heater are the other two better heaters.

Can Fish Do Fine Without A Heater?

Depending upon the type of fish, fish may live without a heater. Hence, you should know about your fish type. There are some fish which can swim well in cold water. Like, Comet Tail goldfish, White Cloud, and dragonfish are few fish that would not require a heater. These fishes easily cope with the drop in temperature.

Can A Fish Tank Heater Catch On Fire?

Yes, things that can heavily catch fire are the heater, the filter, and the lighting as they are connected to electricity.

Overheating of aquarium heaters will lead to the explosion of glass tubes. Although, it is less likely to happen because the heater is designed to be heatproof and submerged in water.

Does Temperature Affect The pH Level?

Yes, temperature plays a vital role in pH measurement. As temperature rises, vibration molecules increase, as a result, water ionizes and form more hydrogen ions. Hence, the pH drops. Therefore, a new pH level is detected in different temperatures due to the chemical and molecule reaction.


The adorable pet, fish needs more care than others as it lives in a different environment i.e, water. Hence, the frequent change instability of water temperature may affect your fish.

A stable water temperature with an ideal range is important for your fish safety and your peace of mind. Therefore, you would better be prepared for warming your fish in a cold environment.

I have mentioned how to heat your tank in different scenarios. Such as a heater malfunction, a power cut or you end up with no heater, all of the solutions would help you in the future for your uncertain situation. Besides, you can check upon the ideal temperature for your fish type to help your fish thrive in any season.

But, I recommend you to have a well-set aquarium with a heater and other necessities for your comfort and fish as well.

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