Do Guppies Need A Heater? (Answered once and for all)

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Do Guppies need an aquarium heater? Yes, guppies are a species of fish from tropical climates and as such, they do need a heater in their aquarium. Guppies need to be kept at between 72°F and 80°F (22°C and 26°C). When kept at lower temperatures, guppies can be susceptible to stress and diseases.

Guppies are often recommended as the first fish for new fish keepers. It is easy to see why. With their bright colors and apparent ease of care, they do indeed make a great choice for those starting out in the hobby.

I have been keeping, breeding, and studying guppies for nearly 3 decades. Over that time I have experimented with water temperatures to find the optimum temperature for booth keeping guppies and breeding them. I have written countless articles about guppies over the years. They are by far my favorite fish!

Why Do Guppies Need A Heater?

Guppies originate from the northeast, South America. Their natural environment is rivers and streams in tropical regions. This, however, is not the main reason guppies need an aquarium heater. 40 or 50 years ago, guppies were extremely hardy and found adapting to new environments relatively easy.

In the last 20 or 30 years, however, guppies have been intensively reared and inbred to form an almost limitless variety of colors and tail shapes. This constant inbreeding has left guppies, in general, much less hardy and less adaptable.

This problem is further compounded by the ultra-clean environment some guppies are bred and raised in. Some of the farms, particularly in the Far East, are of such a high standard, and the water is so warm and clean, the guppies now require those conditions to thrive. They have lost their ability to adapt.

What Temperature Should A Guppy Aquarium Heater Be Set To?

I have found the best temperature to keep guppies at is between 72°F and 80°F (22°C and 26°C). The best way to achieve this is to set your aquarium heater to about 78°F (25°C).

Most aquarium heaters are not known for their accuracy (except the Fluval E Series Heaters which you can find out more about in our article on the E Series Heaters).

By setting the heater to slightly lower than the guppies maximum suggested temperature, you allow for slight variations in the accuracy of the heater’s thermostat. All aquariums should be fitted with a good quality digital thermometer just so you can keep an eye on the water temperature.

If you place the thermometer somewhere you can see it every time you visit the tank, you will get an early warning if the water is too hot or too cold.

Are There Any Circumstances Guppies Do Not Need A Heater?

If you live in a part of the world where the ambient temperature is naturally high enough, or the room temperature is kept warm enough, that the water temperature never drops below 72°F (22°C) then you probably won’t need a heater.

However, for peace of mind, you should still put one in. The heater won’t come on if the aquarium water is warm enough, but if the temperature ever dips, the heater will kick in and keep your guppies happy.

What Type Of Aquarium Heater Should I Use?

There is a whole raft of aquarium heaters on the market. I have had great success with heaters you place inside the aquarium, so-called submersible heaters, but you can also get canister filters with built-in heaters, heaters that fit in the return pipes from a canister filter as well as heaters that are buried in the substrate.

To find out more about the aquarium heaters I have used and recommend, why not have a look at my Recommended Gear page.

Does The Actual Water Temperature Affect Guppies?

I have found the lower the water temperature, the slower pace of life the guppies live at. If you keep your water temperature at and around 72°F (22°C), the guppy’s metabolism runs slower.

This means they grow slowly and babies take longer to develop inside the females. The ultimate result is the guppies will live longer.

If you keep your aquarium water at the upper end of the temperature range, the guppies metabolism will run much faster. The result is that your guppies will grow quickly and babies will develop quicker, meaning you can produce more fish over the course of a year. The downside is however that, generally, guppies kept at high temperatures don’t live for as long.

Can Guppies Be Too Warm?

Yes, guppies can be too warm. If you are keeping Discus or German Blue Rams, both species will do well in water which can be up to 86°F (30°C). Guppies however will struggle at these temperatures.

Firstly, guppy’s metabolism will be running extremely high, which means they will live fast and die young. Secondly, warm water holds less oxygen than cool water. At very high temperatures, guppies may be seen ‘gasping’ at the surface as they struggle to get enough oxygen out of the water.

In Conclusion

In answer to the question Do guppies need a heater, the answer is yes, guppies do need a heater in their aquarium. Without an aquarium heater, you run the risk of the water temperature dropping too low which will leave the guppies susceptible to stress as well as pests and diseases. A stressed guppy will be weak and probably short-lived.

About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James

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