Guppies are ‘tropical’ fish. They need to be kept in warm water to grow and thrive. The ideal temperature for a guppy aquarium is between 75°F and 80°F (23°C and 26°C). For short periods of maybe 1 or 2 days guppies can be kept as low as 65°F (18°C). For longer periods, the minimum temperature for a guppy aquarium is 72°F (22°C).
Guppies are bright, colorful, and hardy. They are probably one of the most popular fish in the freshwater fish-keeping hobby. Guppies have been kept and selectively bred since the 1960s and are now available in a wide variety of colors and tail shapes. I kept my first guppy more than 30 years ago, and I have enjoyed keeping and breeding them ever since.
Do Guppies Need A Heater?
As mentioned, guppies need the water temperature to be between 75°F and 80°F (23°C and 26°C).
Whether or not the aquarium needs a heater will depend on the ambient temperature in the area you live. If you live in Texas or Florida for instance, you may well find your guppies don’t need a heater. If however, you live in Montana, you almost certainly need a heater.
An aquarium heater’s job is to raise the water temperature above the ambient temperature sufficiently to keep the aquarium inhabitants comfortable.
I have written many articles about whether or not guppies need a heater, including this one which is titled Do Guppies Need a Heater?
Consequences On Guppies Of Low Water Temperatures
If your guppies are subjected to low water temperatures for a prolonged period of time, the stress will start to take effect on the guppy’s health.
Water temperature affects guppies metabolism, growth, and development. When the temperature is too low, your guppy will struggle to digest their food and they will become more susceptible to pests and diseases.
Can The Water Be Too Warm For Guppies?
The water temperature in a guppy aquarium should never go much higher than about 78°F to 80°F (26°C to 27°C). If the temperature goes much beyond 80°F the temperature will again cause your guppies stress.
When the temperature exceeds 80°F your guppy’s metabolism will be going like the clappers! Even if the stress of such warm water doesn’t cause your guppy to die, its life will be severely shortened.
Low Water Temperatures During Water Changes
If like me, during water changes you just use cold water straight from the tap, your aquarium water temperature will naturally drop.
For the very short period between you adding new, cold water and your heater bringing the water up to the correct temperature, the guppies will be unaffected. In the wild, water temperatures will naturally fluctuate, especially during periods of heavy rain or localized flooding.
Guppies are tropical fish. They rely on us to keep their environment suitable and stable. This includes making sure the water temperature is right.
Guppies can tolerate low water temperatures for short periods of time. If the temperature drops very low for a couple of hours, say during a water change, your guppies will be unaffected. If the temperature is a little lower than normal for a couple of days, say following a heater failure or during a long power cut, the guppies will be fine. If the temperature is too low for a prolonged period of time, your guppy’s health will suffer and they may even die.