Water temperature is one of the important parameters in keeping guppies. As tropical fish, guppies prefer warm water. If you live in areas where the temperature drops below 74 °F (23 °C), you probably need a heater in the guppy tank.
Guppies thrive in warm water at 72-82 °F (22-28 °C). Too cold water affects their metabolism, making them sluggish and sick. An aquarium heater with a good thermostat helps maintain water temperature in a comfortable range.
Facts: Do guppies need a heater?
Thermoregulation is a problem for all cold-blooded animals as they cannot produce enough heat during a cold to keep their bodies warm. Fish usually rely on the natural heat from their environment to survive.
Guppies are tropical fish that thrives in warm water. They prefer a temperature range of 72-82 °F. Rapid temperature changes are likely to complicate their life. Cold water makes a guppy lethargic, sick, or even die. Check why pregnant guppies keep dying.
Heaters in a guppy tank are essential for keeping water temperatures safe. Aquarium heaters with a thermostat can self-regulate based on preset settings, regulating and maintaining constant aquarium water temperatures.
A sudden change in water temperature is also not healthy for guppies. A sharp drop or rise in temperature may shock the fish resulting in a fatality. This is likely to happen when you don’t have a heater in the tank or when changing the water.
NOTE: It is important to install the heater closer to the filter to help circulate the warm water evenly in the tank. A large tank may need two heaters positioned opposite each other.
Heater size suitable for guppies
Using the right heater for your tank size is critical to the equipment’s efficiency and your fish’s safety. Your guppy tank size will determine the kind of heater to use. As a rule of thumb, use a 5-Watt heater per gallon (4 liters) tank.
| Tank Size | Heater wattage |
| 5 Gallon (19 Liters) | 25 W |
| 10 Gallon (38 Liters) | 50 W |
| 20 Gallon (76 Liters) | 100 W |
| 25 Gallon (95 Liters) | 125 W |
| 40 Gallon (151 Liters) | 200 W |
| 50 Gallon (189 Liters) | 250 W |
| 65 Gallon (246 Liters) | 2 X 200 W |
It is important to use a heater as directed by the manufacturer. Read and follow the instructions in the owner’s manual.
Can guppies survive without a heater?
In tropical regions, guppies will survive pretty well without a heater. These regions feature warm temperatures year-round. If push comes to shove, guppy fish can survive in lower-temperature water that goes as low as 60 °F, but they won’t be happy.
In very cold water, guppies will become sluggish and may even stop eating. This will definitely weaken their immune system. As a result, the fish may get attacked by a number of infections, such as fin rot, swim bladder, and dropsy.
Can guppies survive in cold water?
Guppies cannot survive in cold water since they are tropical fishes. They prefer water temperatures between 72°F and 82°F. Most aquarium tanks with guppies will require an aquarium heater to maintain a comfortable temperature for the fish.
Guppies are quite hardy and can withstand temperatures as low as 68°F, but anything below that is too cold to survive. However, this won’t take long before they develop health problems and eventually die.
How do you keep guppies warm without a heater?
Without an aquarium heater, you may capitalize on your HVAC heating system. The aquarium water will eventually absorb heat from the surroundings and become comfortable for the guppies.
Raising the tank to a better elevation in the room can also lead to a heat flux of at least a few degrees warmer, as upper levels are typically much warmer. Finding a position in the room where the tank will receive at least six hours of natural sunlight every day can also yield decent results.
Furthermore, each room has warmer and cooler parts, which an aquarium owner can exploit to his or her advantage when attempting to work without a heater. Placing an aquarium in a warmer, insulated spot will provide it with extra heat without much effort.
References: Aquatic Community: Guppy Fish, Aquarium Kids: Guppy Care Sheet and Aquarium science: 14.8. Aquarium Heaters
