Yes, guppies most certainly do need a heater and heated water as they are tropical fish that are used to living in high temperatures. Guppies' water temperature cannot drop below 68°F (20°C), otherwise, you risk serious health repercussions for your fish, and whilst it is achievable to reach this temperature without a heater, it will most likely not be consistent enough to risk it.
A heater for your guppy will not only keep the water temperature where it needs to be in order for your fish to live a long and healthy life, but it keeps consistency within your fish tank, which is what guppies really need from their environment.
What Temperature do Guppies Need?
Guppies need to reside in water temperatures that range between 74-82°F (23-28°C). So, can guppies live without a heater? Sure, they can be kept in temperatures as low as 68°F (20°C), and slightly higher than 82°F (28°C), which is achievable without a heater, but it is not recommended as it will likely compromise their immune system, stunting their growth and coloration, whilst making them more susceptible to illnesses.
Heater Wattage Guide for your Guppy Tank
You can calculate the wattage you need for your heater via this wattage to gallon ratio created to simplify what kind of heater you need for your guppy tank. The following calculations are for home aquariums with an average room temperature of about 70°F (21°C):
- 5 Gallons (20 Litres) = 25 Watts
- 10 Gallons (40 Litres) = 50 Watts
- 20 Gallons (80 Litres) = 100 Watts
- 25 Gallons (95 Litres) = 125 Watts
- 40 Gallons (150 Litres) = 200 Watts
- 50 Gallons (190 Litres) = 250 Watts
- 65 Gallons (250 Litres) = 2 x 200 Watts
- 75 Gallons (285 Litres) = 2 x 300 Watts
By following this guide you can easily acquire the perfect sized heater for your tank to keep your guppies at the right temperature!
Do Guppy Fry Need a Heater?
When discussing whether or not guppies need a heater and what temperature they require, it is equally as important to look at their fry and their requirements. Guppy fry will need a heater to keep them warm and their body heat consistent, just like adult guppies. The ideal temperature for your guppy fry should be between 76-80°F (24-26°C), and the same applies to pregnant guppies.
When you are looking for the perfect spot to place your heater within your guppy aquarium, make sure you keep it as close to the filter as possible. The filter will help circulate warm water around your tank, speeding up the heating process and making sure the hot water has been distributed around the tank evenly. By not having the heater next to your filter, you may find that some areas of your tank are significantly colder than others.
Large Tank Heater Placement
If you have a large tank that will require two heaters, you should place one heater next to the filter and the second one on the opposite side of the tank. This will ensure that the heat is being distributed evenly throughout your tank.
Guppy Tank Temperature Changes
Extreme temperature changes within your tank should not occur once you have installed a heater, however, it is possible. The most important thing is to recognize when your guppies are experiencing temperature increases or decreases and resolve the situation immediately.
What Will Happen if the Water Temperature Gets too Low?
If you do not heat your guppy tank correctly, allowing the water temperature to plummet, your guppies will suffer some serious side effects. Guppies, when the temperature first starts to drop will appear visibly slow and lethargic. They are cold-blooded fish, so their body temperature will match that of their environments.
This will cause an abundance of stress on their bodies, which makes them unlikely to accept food, weakening their bodies and immune system. Guppies do not usually reside at the bottom of tanks, however, if they are undergoing serious stress and are unwell from temperature decreases, you will likely find them swimming around there. This can be problematic if you have a large community tank with predatory fish residing at the bottom.
Typically, if the temperature does not rise your guppy will adopt many illnesses and diseases due to their weakened immune system. Common guppy diseases include fin rot, swim bladder disease, and dropsy. Unfortunately, these diseases can become fatal.
What Will Happen if the Water Temperature Gets too High?
You don't just need to worry about the temperature getting too low in your guppy tank, you also need to concern yourself with the temperature becoming too high and ultimately too hot! Fortunately, it is far less likely for your tank to overheat rather than become too cold, but it does happen.
Extremely hot water will likely result in erratic behavior from your guppy, typically in the form of them darting around in different directions, and displaying far more energy than usual. This extra energy that they need to burn off is caused by the unnaturally warm water and it massively stresses guppies out, which will result in a weakened immune system, increasing their susceptibility to illness and disease.
Fortunately for us hobbyists, it is far easier to cool a tank down than it is to heat it up. By just adding more conditioned cold freshwater to your tank and having a fan blow on it until it has cycled through the entire tank, distributing the cool water everywhere, you should be good to go!
Sudden Temperature Changes
If for whatever reason you have decided against using a heater for your guppy tank, you will likely experience sudden temperature changes due to the instability and inconsistency of your guppy aquarium water. Sudden temperature changes are incredibly detrimental for your fish and other tank inhabitants and guppy tank mates.
The first thing that could happen if your tank experiences a sudden temperature drop is temperature shock. This is when your guppy fish go into a state of shock due to the quick and unforeseen temperature decrease, which can result in your guppy dying within minutes. If they do not die they can go into a coma, causing permanent damage.
The second circumstance as well as temperature shock is respiratory issues. Your guppies will almost certainly suffer from this if they experience extreme temperature changes, most commonly occurring when the tank temperature increases too much. When the water gets too hot, it will lose oxygen, which results in your guppies having a much harder time breathing, and, if left too long, they will eventually die.
Temperature Guage (Do Not Rely on Your Heater to Tell the Temp)
The majority of heaters, especially the high-quality and highly rated ones will usually tell you the exact accurate temperature of the water in your tank. However, you should still use a thermometer to double-check the temperature of your tank, keeping things consistent. After all, it is better to be safe than sorry.
Yes, guppies need a heater, and the main takeaway from this should be that you cannot let your tank water become too hot or too cold, as it will cause a plethora of problems for your guppies. Regular temperature checks are certainly required, and you should also double-check your tank's temperature regularly, not only relying on what your heater says.