Do Guppies Need A Heater? We Warm Up On Why They Need One.

Do Guppies Need A Heater
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Guppies are tropical fish that live in warm waters while in the wild. Today, these fish are not just limited to living in the tropics. They have adapted and can survive in different environments. 

But do guppies need a heater? Yes. They need warm water to lead a healthy life. And that’s not all. 

This article discusses why guppies need a heater, the types and correct wattages of heaters, and the effects of not maintaining constant water temperature.

Keep reading. 

Why Do Guppies Need A Heater?

Guppies are native to the streams and rivers of South America. The waters in these tropical regions are quite warmer, unlike other regions in the world.

If you do not live in the tropics, a water heater is must-have equipment for guppies. The heater will help replicate the same temperature present in the wild. 

Additionally, guppies need a water heater because they are no longer the hardy species they once were. 

The intensive selective breeding of guppies to produce unique and vibrant colors, patterns, and tails has left them less adaptable to changes in water temperature. 

Moreover, most hatchery farms maintain high-quality water standards when breeding guppy fry. When guppies are bred in such warm and clean environments, they need the exact conditions to thrive. 

When you get a water heater, it warms the aquarium water because water heats rather slowly than air. The heater maintains the ideal water temperature your guppy needs to thrive. 

But what is the ideal temperature for these aquarium fish? 

What Is The Ideal Water Temperature For A Guppy Fish Tank?

The best temperature for guppies is between 72 and 80 degrees Fahrenheit. As tropical fish, guppies need warm aquarium water.

However, it should be noted that these fish can adapt to slight changes in temperature. These fish will be fine if the temperature drops or rises above their preferred temperature range on occasion. But, if they are constantly exposed to extreme heat or cold, they may get stressed and sick. 

Guppy Aquarium Heater Size Chart

Having established that guppies do need a heater to live happily, you must understand the correct wattage for your guppy tank. The general rule of thumb states 5 watts for 1 gallon of water volume. 

Here is a guppy aquarium heater size chart to help you find the best heater wattage for your aquarium. 

Tank SizeHeater Wattage
5-Gallon25 Watts
10-Gallon50 Watts
20-Gallon100 Watts
25-Gallon125 Watts
40-Gallon200 Watts
50-Gallon250 Watts
75-Gallon 600 Watts (2 x 300 W)

The above water heaters are preferable for indoor guppy fish tanks whose room air temperature is 70 degrees. 

4 Types Of Aquarium Heaters For A Guppy Tank

There are four types of aquarium heaters you can add to your guppy tank. However, not every heater is suitable for your tank set-up. Read on to find the best type of heater for your guppy tank. 

1. Submersible Heater

Submersible Heater

The submersible heater is submerged in water to heat it. The heater is more effective when positioned at a vertical or horizontal angle. It takes the correct water temperature reading at these angles. 

2. Hang-On Heater

Hang-On Heater

As the name suggests, these heaters are hung on the back side of the guppy aquarium. They feature a glass tube with the heating element that you dip into the water. Nevertheless, always place the controls above the waterline. 

Hang-on heaters are preferable for freshwater tanks. You run the risk of corrosion and electrical shock when put in saltwater aquariums.  

3. Substrate Heater

Substrate Heater

The substrate heater is installed in the substrate. They mainly have two advantages:

  • They are not visible.
  •  They heat the water uniformly.

These aquarium heaters will maintain the ideal temperature in guppy tanks with live plants. 

4. Filter Heater

Filter Heater

Like substrate heaters, filter heaters are also invisible. Their invisibility reduces the likelihood of your guppies destroying it. Filter heaters work best in bigger tanks. 

What Happens When Guppies Live In Very Cold Water?

Guppies thrive in a tropical climate with warm water. But what happens if the aquarium water gets too cold? They may get stressed, sick, or die. 

If the tank water temperature drops below 68 degrees F, your guppies may become sluggish and inactive. These aquarium fish will not generate the much-needed heat to swim and move around. Also, the cold water will limit your guppies’ breeding capabilities.

This species needs warm water to breed, and the cold temperatures will mean reduced guppy fries. 

Moreover, these tropical fish will get stressed living in a cold environment. Stress can lead to aggression, weakened immunity, infections, and death. Cold temperatures can also result in severe health complications. 

Lastly, colder temperatures lower a guppy’s growth rate. Cold water affects the development of organs and the metabolism rate. As a result, guppy fish appear dull, have a weakened immune system, and have a short lifespan.

What Happens When Guppies Live In Hot Water?

Hot temperatures (above 85 degrees) are also harmful to guppies. Overheating the guppy tank can result in reduced fertility. The excess heat lowers sperm count in male guppies, decreasing reproductive success. 

High temperatures also weaken guppies’ immune systems. Overheating can lead to autoimmune diseases, infections, and lysosome overproduction. In addition, hot temperatures can cause suffocation since hot water has fewer oxygen levels. 

If you do not have a thermometer to check the water temperature in your indoor aquariums, observe your guppies’ behavior. 

Cold and hot water temperatures can stress a guppy. When this happens, your guppy may exhibit the following signs:

  • Rapid movement of gills
  • Swimming to the surface to get air
  • Reduced activity, lethargy, and sluggish movement
  • Reduced appetite

What should you do after making the above observations? Test the water temperature and correct it. 

How Should You Test The Water Temperatures For A Guppy Tank?

The two best methods to test the ideal water temperature is through your hand or a thermometer. Put your hand into the fish tank to ascertain whether it is hot, cold, or lukewarm. 

The best water temperature for guppies should feel lukewarm. However, this method will not outline the exact water temperature. 

Due to this, we strongly recommend getting a thermometer. A thermometer, whether traditional or a suction cup thermometer, is foolproof and accurate. 

What Happens When Guppies Are Exposed To Sudden Temperature Changes?

Guppies can adapt to cool and warmer waters. However, they are quite sensitive to sudden temperature changes

Guppies may go into shock from a sudden drop in temperature. Temperature shock can lead to death or a comma that causes irreversible permanent damage.

On the other hand, a sudden increase in water temperature can lead to respiratory problems. Warmer water has reduced oxygen levels, and guppy fish need air to live. The guppies may gasp for air for a few minutes and then die.   

Do Guppy Fries Need A Heater?

An adult guppy needs a heater. What about a guppy fry? Yes. Unlike adults, guppy fries have a lesser coping mechanism for cold. 

Their bodies are incapable of holding body heat, meaning their body temperature will match their environment.

What’s more, warm water speeds up their metabolism and growth. The warmer the water, the faster the guppies’ growth rate. Lower temperature water can subject these little fishes to various diseases

Here is a video that explains more about temperatures for guppies:

Frequently Asked Questions

Can I Keep Guppies Outdoors?

Yes, if you are keeping them in a tropical climate. You do not need a heater here because the sun acts like one. You do not have to worry about adding a heater at night because water cools more slowly than air, and the temperatures will not harm your fish. 

Do I Need A Spare Heater?

It would be best if you had one. Emergencies are random, and having a spare heater will mean keeping guppies happy and alive. 


The answer to the question – do guppies need a heater – is a resounding yes! Guppies cannot flourish without a heater. Therefore, invest in a high-quality water heater. The aquarium heater will maintain the same temperature your guppies are accustomed to in the wild. Getting a heater will also keep your guppies happy and healthy.

Last Updated: July 28, 2022

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