What’s The Best Water Temperature For Guppies?

by | Blog, Freshwater Fish

1. What Water Temperature Do Guppies Need?

Otherwise known as a guppy, poecilia reticulata is a hardy little fish native to northeastern South America and the southern Caribbean. Guppies easily adapt to diverse environments and are found in a variety of biotopes. In the wild, guppies live in a warm, freshwater environment – Which is why in an aquarium, guppies need a heater.

Wild guppies live at temperatures around 64 to 82 degrees Fahrenheit, but these species are very rarely used as aquarium pets. The guppies (including fancy guppies) commonly sold at stores are commercially bred. Because these new variations aren’t as hardy as the wild guppies, they need a more controlled environment, with an ideal temperature of about 76 to 78 degrees Fahrenheit.


Fancy guppy


Since these fish come from a tropical environment where the temperatures are warm, guppies need a heater (unless you live in an area that stays consistently within their required temperatures). Here’s the best water temperature for guppies:




Before we dive more deeply in to the important details, please note that any fish will experience shock if you change the water temperature too much or too quickly; Consistent temperature is mandatory.

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2. Can Guppies Live in Cold Water? Minimum Temperature Guppies Can Survive In

No. Guppy fish are cold-blooded tropical fish that evolved to live in warm climatic regions, so they must not be kept in water below 72°F.

Guppies may survive in temperature ranges below 72°F as low as 60°F (16°C), but just because they can doesn’t mean they should have to, and it’s not without consequences. Keeping guppies in fish tanks with water below minimum water temperature can make them susceptible to disease, and is stressful – Inviting several other problems (see below!)

2.1  Effects Of Colder Water on Guppy Fish

As a poikilothermic species, guppies are highly dependent on external temperature for regulating their body processes. Poikilothermic animals maintain a body temperature similar to their surroundings. If the water or air temperature around them is too low or too high, their body temperature will change accordingly (unlike humans).

For guppy fish, cold water slows down their physiological functions including their digestive systems, growth, and reproductive activity. This has several repercussions, which we’ll take a look at next.

2.2  Cold Water Makes Them Prone to Developing Diseases

Pink and orange guppy

If guppy fish are kept at temperatures below 72 degrees Fahrenheit, they’ll become susceptible to disease. A common example of this is the protozoan illness frequently referred to as “guppy disease,” due to its predominance in guppies. This illness typically flourishes in unclean water or if the aquarium water temperature is not within the correct range.

Other examples include ich, and parasite problems – Both of which are more likely to pop up if your guppies are kept in incorrect water temps.

2.3  Cold Water Slows Growth Rate

If the tank falls below the ideal guppy water temperature, they’ll experience weakening of the immune system, lethargy, and stress. Cold water also adversely affects their growth rate, causing juveniles to take longer to reach adulthood.

2.4  Cold Temperature Affects Breeding

For guppies, reproduction slows down and stops in low temperatures because their metabolic rate and energy decreases, negatively affecting their ability to produce and care for offspring. Even if guppies do breed in cold water, the fry may not survive, as they need warmer water between 76°F to 80°F for growth to adulthood.

3. What If Guppies Stay in A Tank That’s Too Hot? Maximum Temperature Guppies Can Survive In

Out of whack temperatures cause stress to guppies, and water that’s too warm is no exception. They can suffer metabolic stress, disease susceptibility, shortened lifespan, and suffocation as a result.

When water temperature increases, the amount of dissolved oxygen in the water decreases. Water temperatures above 82 degrees Fahrenheit are too hot for guppies to bear; At this range, they begin to suffocate due to the lack of oxygen in the water, leading to premature death.

3.1  Hot Water Increases Metabolic Rate

Remember how I mentioned earlier that fish are dependent on their environment to maintain their body temperature? Well, when the temperature increases, the chemical reactions in their bodies that are responsible for metabolic processes increase too, speeding up their metabolism.

When their metabolism speeds up, they require more energy just to stay alive.


Rummy nose tetra and guppy


This increase in metabolic rate causes them to grow more quickly, but it’s not without drawbacks: It also causes significant stress to the fish, which you may see in the form of hyperactivity in the tank. Stress is the top killer of aquarium fish, and can lead to a host of other health issues for the fish.

3.2 Hot Water Makes Them Reproduce More Quickly

Because hotter water temperatures stimulate the guppies’ metabolism, it also causes them to reproduce more quickly and more frequently. I’d recommend a breeding tank temp of 76-78°F; Any higher than that, and you’ll start to see increased susceptibility to disease, parasites, and other stressors, which will have negative effects on their survival and reproductive success and ultimately cause a much shorter lifespan.

3.4  Hot Water Reduces Oxygen Levels

The hotter the water temperature, the lower the dissolved oxygen level will be for your guppies – And they can’t survive without oxygen. If the temperature is too high, they’ll suffocate because they can’t get enough oxygen from the water.

Other than difficulty breathing, another issue here is that the beneficial bacteria that helps keep your tank cycled and healthy by eliminating ammonia won’t be able to flourish properly.

4. What To Do If the Water Is Too Hot in the Guppy Tank

Typical behavior for guppies in water that’s too hot is hyperactivity; You’ll see them start to whizz around the tank unnaturally. This is a red flag that something’s wrong, and it can be disastrous for your guppies.

To cool the tank water, place a fan to blow over the water’s surface to bring the water and air heat down within an ideal temperature range. Floating ice packs on the water surface will also work. You may also consider a proper aquarium chiller, especially if you live in an area where it gets very hot regularly (such as hot summers).

Lastly, you can do a partial water change with cooler water.

5. What To Do If the Water Is Too Cold in the Guppy Tank

Aquarium thermometer: Water temperature


If the tank temperature starts to drop below the minimum water temperature required for your fish, then you need a heater.

Unless you live in a very warm climate that doesn’t fall below the guppies’ ideal temperature range of 76-78°F, your tropical fish tank will require a heater to maintain the correct temperature. The minimum water temperature for these fish is 72°F, so that’s about the lowest the outside temp should get without one.

Remember that the heater you choose depends on the size of the fish tank. To ensure the correct temperature, keep a thermometer in the tank.

Options for submersible heaters include HOB (hang-on-back heaters), substrate heaters, and filter heaters. I recommend installing your heater near the filter, as the filter helps circulate the warm water, helping to maintain a consistent water temperature throughout the tank.

6. Will Changing the Guppy’s Water Affect the Temperature? How to Maintain Water Temperature During Water Changes

Changing the water can change the water temperature; It depends on the temperature of your water supply, which is typically affected by outside temperature.

You can turn on your water and mix the temperature using the hot and cold valves, and test it using a thermometer until you get it within range for your fish.

It also depends on your intent. If you need to adjust the fish tank water temperature in one direction or another, you can use the temperature of your water supply to help you so do (like adding cold water to cool down a tank).

To maintain water temperature during water changes, check the tank temp first, then test it against the temp of your water supply. Adjust the mixing valves on your faucet until you’re able to get it within the optimal temperature range. Perform the water change slowly, a little at a time, to allow the fish to adjust.

If you don’t have access to a warm water valve, you can use an extra aquarium heater to raise the temperature of the new water in a separate container before adding it to the main tank, so that you keep a constant temperature and the fish don’t experience any fluctuations.

7. What Temperature Do Guppies Need: FAQs

Green and orange guppy

7.1  Can You Keep Guppy Fish in An Outside Pond?

Yes, you can keep a school of guppies in an outside pond in the garden, but only if you live in a tropical climate where the water temperature range can stay optimal for guppies. You can mitigate a little fluctuation in outside air temperature by using a heater, but this is limited.

Also keep in mind that guppies jump! As a result, it’s best to cover ponds with a net; This saves the fish from predatory attacks (neighbor’s cats, etc.) and prevent them from jumping out. It can also help keep falling leaves and twigs out of the pond, making the filter more effective.

7.2  Which Other Fish Can Live in The Same Temperature Water as Guppies?

The ideal water temperature for guppies is 76 to 78 degrees Fahrenheit, which is ideal for many common tropical fish who also need warm water. This range is a suitable temperature for fish such as mollies, swordtails, and platies.

7.3  What Is the Ideal Water Temperature for Breeding Guppies?

This particular species of tropical fish is renowned for their ability to breed successfully. They are prolific reproducers! To encourage breeding, you can increase your tank temperature by 2-3 degrees for a brief period.

The ideal temperature for guppies to reproduce is 76-78°F; Just remember that it’s essential to avoid exposing the fish to temperatures exceeding 82 degrees Fahrenheit as this can be detrimental to their health.

8.  Conclusion

Guppies prefer warmer water temperatures ranging from 72 to 82°F (22-28°C). Even though these fish may be able to survive in colder or warmer water than this, they’d suffer as a result, so keep the temperature within the recommended range. The good news is that there are many other fish popular in aquariums that will pair well with these warmer temperature ranges; In fact, some of the most common tropical fish like mollies and platies can live in these water temperatures.




To say that I’m obsessed with all things saltwater is a bit of an understatement. Aquarium Passion has served freshwater and saltwater aquarium hobbyists for over 10 years, and I'm committed to keeping the information accurate and free. My post-bac certification in Sustainability informs my writing about aquarium conservation efforts. When I'm not writing at AP, I'm out in the ocean or researching weird fish.


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