Do Guppies Need A Heater? (Ideal Heater Types + Wattages)

Image of an aquarium with a heater

Guppies need a heater. Their body needs to stay warm at all times for them to live a long and stable life. A heater ensures that the aquarium’s water temperature is always ideal for the guppies. If guppies are exposed to cold water, they will fall sick and may even die because of it.

Let’s now understand in detail the ideal water temperature for guppies and why a heater is essential.

What Is The Ideal Water Temperature For Guppies?

Guppies are tropical fish and thrive in warm water.

The ideal water temperature range for guppies is 72°F to 82°F (22°C to 28°C).

However, they can withstand a slight change in temperature.

Guppies can survive at a lower temperature of up to 60°F.

If the water temperature falls further, it could make your guppies feel sluggish and sick. This can be life-threatening.

So, it is crucial to maintain the desired water temperature for the good health of guppies.

Alright! Now that you know guppies need a heater, let’s talk about the ideal heater size for your aquarium.

Guppy Aquarium Heater Size Guide

The size of your aquarium will determine the heater size.

If you have a small tank, you will require a heater with less wattage.

Similarly, the heater should have more wattage for a large tank to ensure that the water gets heated properly.

You need to follow a basic thumb rule while selecting the wattage of the heater.

The rule is approximately 5 watts per gallon of water in your tank.

The below table lists the heater wattages needed for various sizes of indoor aquariums.

Note that the room air temperature is considered to be 70°F (21°C).

Aquarium SizeHeater Wattage
5 Gallons / 19 Liters25 W
10 Gallons / 38 Liters50 W
20 Gallons / 76 Liters100 W
25 Gallons / 95 Liters125 W
40 Gallons / 152 Liters200 W
50 Gallons / 190 Liters250 W

Using the tank sizes and heater wattages mentioned above, you can heat the tank water up to 80°F (27°C).

What Type Of Heater Can You Use For A Guppy Tank?

While selecting a heater for the guppy tank, you must consider the aquarium size.

There are four kinds of heater that can be used for a guppy aquarium.

Submersible Heater

A submersible heater is installed below the waterline. It is made up of either glass or durable plastic material.

Glass heater is fragile, and it needs gentle handling as it can easily break if it is handled roughly.

Plastic heater, on the other hand, is more durable and hence preferred by many aquarists.

A submersible heater can be positioned at any angle in the water.

A horizontal or vertical angle is the best position as it allows the internal thermostat to take an accurate reading of the water temperature.

Besides, this heater has a suction cup that enables it to hold on to the aquarium glass firmly so that the heater does not float in the water.

Hang-On Heater

Hang-On heater is the most common as it is cheap as compared to other aquarium heaters.

It usually comes with the starter aquarium kit, or you can purchase it from any of your local pet stores.

Unlike the submersible heater, the hang-on heater hangs on your aquarium’s top edge, usually on the backside.

It has a glass tube containing the heating element which dips into the aquarium water.

This heater is not advisable for saltwater aquariums as the salt can get into the tube and cause electrical shock or corrosion.

Substrate Heater

As the name suggests, a substrate heater is installed below the substrate.

It is mainly used in tanks where live plants are kept along with fish.

When this heater is activated, the substrate in the aquarium gets heated, and the water becomes warm.

The biggest advantage of the substrate heater is that the water in the aquarium gets heated uniformly.

Besides, since it is immersed inside the substrate, it is invisible and does not change your tank’s appearance.

Filter Heater

The filter heater is mainly used for large-sized aquarium. Just like the substrate heater, this heater is also invisible.

Since it is not visible to guppies, its chances of getting destroyed are minimal.

Now that you know about the various types of heaters, let’s see if guppies can survive without a heater.

Can Guppies Live Without A Heater?

Guppies can live without a heater provided the water temperature is maintained regularly in the range of 72°F to 82°F (22°C to 28°C).

However, it is difficult to manually maintain this ideal water temperature. So, a heater is highly recommended.

If the water temperature in the aquarium gets cold, it will adversely affect your guppies’ health.

Your guppies can fall sick, feel lethargic and cold water can even affect their immunity.

A heater ensures that the water temperature stays warm consistently.

You do not have to bother much about the aquarium water temperature if you have a heater installed.

The bottom line, a heater is highly recommended for a guppy aquarium.

However, some aquarists do not prefer a heater as they live in a tropical climate where the temperature does not drop drastically. But…

What Happens To Guppies If The Water Gets Very Cold?

Guppies cannot survive in chilly cold water for too long.

Guppies are hardy fish, and so they can adapt to a slight variation in water temperature, but not much.

If the aquarium water temperature falls below 68°F, it will start having some impact on guppies.

Guppies will become lazy and sick. They will become inactive, and the cold water will harm their breeding as well.

If the water temperature further falls below 60°F, then guppies will not survive for too long.

It will lead to severe illnesses, and your guppies will eventually succumb to death.

Water temperature needs to be stable for guppies. So, is there any way to test the water temperature?

How to Test Water Temperature Of An Aquarium?

You can use a thermometer to test the temperature of the aquarium water.

You can put the thermometer in the water to check the temperature.

Accordingly, you can decide whether to increase or decrease the water temperature.

There are two types of thermometer. The one mentioned above is the traditional thermometer.

The other type of thermometer comes with a suction cup. You can place it on the side of the fish tank.

With this type of thermometer, you can check the water temperature at any time.

Alternately, you can even determine the water temperature by putting your hand in the aquarium water.

However, this method is not very useful as you will only be able to determine whether the water is hot, lukewarm, or cold.

You will not know the exact water temperature.

So, you will need to make a judgment call on increasing or decreasing the water temperature.

How Do You Know When the Temperature Is Too Hot or Cold?

The water temperature for guppies should neither be too hot or too cold.

It can be deadly for guppies if there is a sudden change in water temperature.

You can determine if the water is too hot or too cold by monitoring guppies for the following signs:

  • Guppies are inactive and lethargic while swimming.
  • They are floating towards the surface of the water.
  • Guppies are finding it difficult to breathe. They are gasping for air, and if you notice them closely, there will be a rapid movement of the gills.
  • They are losing interest in eating and refuse to eat.
  • They fall sick very often.

If you notice any of these signs, you need to alter the water temperature.

Now, although guppies need warm water, overheating the water is also fatal to guppies.

What Happens When You Overheat The Tank?

It is true that guppies thrive and prosper in warm water. However, overheating the tank is not suitable for guppies.

They cannot withstand temperatures above 82°F.

Guppies will suffer from the below problems if the water temperature is very high:

  • Reduced Fertility: If the water temperature is very high, it will impact guppies’ fertility. An increase in temperature tends to reduce sperm motility. The sperms of male guppies will also decrease, and it will have an impact on their reproduction.
  • Suffocation: Warm water holds less oxygen as compared to cold water. The warmer the water, the lesser will be the oxygen levels. Your guppies can suffocate due to lack of oxygen. They need oxygenated water to live a healthy life.

Related Questions

Do guppy fry need a heater? Yes, guppy fry need a heater. The fry being smaller cannot hold the body heat for too long, and so a heater comes to their rescue. Guppy fry need warm water as it helps in speeding up their metabolism.

Do you need a spare aquarium heater? Just like any other electronic device, your heater can stop working suddenly or may need to be replaced. In such cases, a spare aquarium heater comes in handy. You can opt for any relatively inexpensive heater as it’s just a backup for the main heater. However, having a spare heater is entirely your choice.

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