Guppies Need Heaters, Heres Why

Last Updated on July 4, 2021 by cmoarz

You might or might not be shocked to hear guppies do in fact need a heater. At least, if you’re in a region that doesn’t have a high ambient temperature. With that said, for most of us, a heater is an important accessory for our guppies. But there are some things you should know…

Guppies are fairly robust fish and can generally survive unheated tanks. However, there is a reason that we say you should always have a heater in with guppies.

Why do guppies need a heater?

The most important reason is consistency. Guppies and their fry need a consistent temperature with no fluctuations, and the best way to achieve this is with a heater.

Daily temperature fluctuations, even mild ones, cause a lot of stress for guppies.

Not only do these fluctuations cause daily stress, but they can also lead to poor development of the fry and even death if it’s a larger fluctuation (i.e., coming from 60 degrees Fahrenheit up to 80).

Another reason that heaters are important for your guppy tank is that their bodies do not produce enough warmth on their own.

Guppies need heat help from external sources in order to keep themselves healthy and happy year-round.

If you don’t give your fish a heater then you’ll find yourself with dead or dying fish fairly quickly as there is no way for them to regulate themselves without assistance.

The ideal temperature for a guppy and her fry is 76°F, and the range of temperature that is considered safe for a guppy and her fry is 72-82°F (22-28°C). The key is consistency.

How do I know if my guppies need a heater?

If your tank is heated with an ambient temperature of over 78°F (26°C) then you do not need a heater. However, if your ambient room temperature falls below 76°F/24°C then the likelihood that your guppies will get cold and sick increases dramatically.

You will also need to check for consistency. If your tank is swinging by multiple degrees threw out the day, You should consider having a heater installed.

Many fish owners have entire rooms dedicated to their fish that have built-in climate control with no fluctuations.

These people can get away with not having a heater because their ambient temperature is always perfect and remains consistent.

What Happens To Guppies If The Water Gets Too Cold?

A major issue that can happen in a tank with guppies is the water getting too cold. They include:

  • Dropping guppy fry production rates
  • Increased vulnerability to disease, infection, and fungus
  • Lower immune systems, plus they are more likely to become stressed.
  • Death

If the water in your tank falls below 65°F then you should do everything possible to increase it back up into that safe zone of 72 – 82 degrees F (22 – 28°C) (without causing shock). If this is not done quickly enough or if there is a large fluctuation from one day to the next with no heater installed, death will occur. Remember: consistency!

What about in an outdoor pond? Can I still keep guppies in my pond or does it also need a heater?

Guppies are tropical fish (lots of people don’t realize that). So they need to be kept in at decently high temperatures. If you live in an area that is consistently warm then you can keep them outdoors in a pond. However, if the pond water temperature falls below 60 degrees Fahrenheit for any length of time, your guppies will most likely die or suffer dramatically from winterkill.

You can in fact heat a pond with a heater, However, it may not be financially feasible for many people.

The other option is to do what some pond owners do, which is to add a heat catcher to the pond. A simple black tarp can be used to retain a lot of heat and put it back into the water when set up properly.

If you live in an area that has winter weather below 65 on a consistent basis for many months of the year, do not keep your guppies in a pond without a pond heater.

Consider using a smaller tub in lieu of an outdoor pond as well. The smaller tubs (bathtubs, outdoor fish tubs, etc) are easier to heat, usually painted/come in black so they also absorb radiant heat from the sun.

What Type Of Heater Can You Use For A Guppy Tank and what size?

  1. A 3 and 5-gallon aquarium would need a 25-watt heater.
  2. A 10-gallon aquarium would need a 50-watt heater.
  3. A 20-gallon aquarium would need a 75-watt heater.
  4. A 40-gallon tank would require at least 100 watts of power.
  5. A 60-gallon aquarium would need at least 150 – 200 watts of power.

You may need to upgrade your wattage based on what temperature you’re trying to reach. The more degrees you want the more watts you need.

Will a heater increase the lifespan of my guppy?

If you do not have a heater in your tank and the water is consistently around 68-70ºF (21°C) then yes, A heater will increase the lifespan of your guppy to what the average lifespan should be. (Around 3 years).

However, if you do have a heater that fluctuates throughout the day or night it may reduce lifespan. This will depend on how severe of fluctuations there are from one temp to another. So be sure to get a stable and dependable heater.

The more drastic lifespan changer is inconsistency, the higher likelihood of shortened life span due to stress/shock caused by abrupt changes in water temperature.

A stable and dependable heater completely nullifies this. Naturally, this will result in an increased lifespan!

Will a heater make my guppies breed more?

A heater can do nothing to make your guppies breed more unless the tank was already at a none ideal temperature. This is based on the natural environment and what you feed them:

A warmer water temperature may appear to result in increased breeding, but this does not happen with any consistency, and usually just indicates the water was just subpar beforehand.

Guppy females are almost always pregnant with fry. There is very little downtime in between carrying, giving birth, and being pregnant again. So there is no real way to speed it up, as she simply can’t go any faster. Her fry still needs roughly 4 weeks to do her birthing cycle.

How can I keep my guppy tank warm without a heater?

A few ways to keep your aquarium warm without a heater would be to have live plants for the fish to swim around in. Live plants will produce oxygen and carbon dioxide which will help heat up the tank.

Another way is to use an aquarium cover. The cover will circulate the air in the tank and provide heating from the cover of light from lamps or sunshine which will also heat up the water in your tank.

Unfortunately, these methods are not ideal for guppies as the temperature fluctuations in the tank will increase their stress and shorten their life span.


Owner of and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!