Do Platies Need a Heater to Survive?

Platies are tropical freshwater fish, which means they’re accustomed to warmer waters. The ideal temperature range for platies is 72°F- 78°F.

They will survive temperatures slightly below the low end of this range; however, the chances of developing health issues significantly increase in lower temperatures.

High temperatures are also correlated with negative outcomes such as shorter lifespans; therefore, you need to get temperature just right.


This page may contain affiliate links, which will earn us a commission. As an Amazon Associate we earn from qualifying purchases.

Therefore, if you’re looking for your platies to thrive and not only to “survive”, I’d say the answer to your question whether platies need a heater to survive is a resounding yes.

Here’s why:

While you may be able to maintain temperatures stable during the summer, if you live in a region with chilly winters and below freezing temperatures, it’s unlikely that you can offer your platy fish stable temperatures throughout the winter months.

You may not even be able to heat the water to optimal levels unless you blast the heater in your home to higher than what you’d normally set for your own comfort.

Aquarists living in tropical climates won’t need an aquarium heater for their platy fish, but those of us that don’t, will need to set up a heater to maintain water at the required temperature during the months when outside temperatures drop.

Therefore, rather than worrying about the negative consequences of exposing your platies to temperatures that aren’t in their range, I suggest you invest in an aquarium heater.

How to Calculate Heater Size for Platy Fish?

When looking for an aquarium heater, you need to size the heater according to the size of your aquarium. A good rule to go by is to calculate 5 watts per each gallon of water volume.

So, if you have a 25-gallon aquarium, you’ll need a 125-Watt heater to heat up water in the aquarium. Getting a low wattage heater will not be able to efficiently heat up the water and keep it heated.

A heater will help you easily regulate the temperature in the aquarium and will help you avoid sudden changes that could lead to various health issues and even the death of your platies.

Make sure you size your heater accordingly, otherwise you’ll have trouble with heating up water in the entire aquarium to the required temperature.

Keeping Platy Fish Indoor

I mentioned that aquarists in tropical climates needn’t worry about setting up a heater in the aquarium, but that aquarists in non-tropical climates can’t skip a heater.

Now you may argue that your home is perfectly heated to 72-73 F during the winter months, but here’s the catch — air heats up faster than water and the water in your aquarium won’t have the same temperature as the air in your room.

Unless you’re compensating for this difference in water and air temperature, not having a heater is a bad idea, especially that without it you can’t keep temperatures constant in case there are sudden changes in outside temperatures.

There are various fish diseases that can appear during periods when temperature conditions aren’t suitable for your platies or if there are sudden changes in temperature.

Fluctuations in temperature or inadequate temperature can weaken the immune system of your fish, allowing opportunistic parasites and bacteria to cause health problems in your fish.

A heater with a thermostat will help regulate the water temperature in the aquarium, regardless of outside temperatures, and prevent these types of illnesses.

Keeping Platy Fish Outdoor

If outside temperatures during the winter months in your region don’t drop below 68 F, you can continue keeping your platy fish in an outdoor pond even during the winter months. Just like water takes time to heat up, it also takes time to cool down.

What if you don’t live in a tropical climate? Can you still keep platy fish in outdoor ponds or tubs? Yes, you can, but only during the summer months.

During the winter months, you should move your platy fish indoors, where you can heat their water to the required temperature.

Health Effects of Uncontrolled Water Temperature

As I mentioned before, having water temperature in the aquarium that’s uncontrolled can lead to temperature fluctuations that will have adverse effects on your platies.

In the wild, fish can behaviorally thermoregulate, which means they can seek out waters with temperatures that’s physiologically optimal for them.

Since space in an aquarium is limited, they cannot seek out waters with temperature that is suitable for them, which means that they rely completely on you regulating the temperature in the aquarium.

If temperature that’s optimal for their physiological needs is not available in the aquarium, there will be health consequences that may be difficult to overcome once they occur.

Make sure you research the optimal temperature for the type of platy fish you’re planning on keeping and do your best to recreate it even if that means spending extra on a heater.

Fish that aren’t offered the right temperature conditions go through thermal stress, which compromises their immune system and is correlated with a higher susceptibility to diseases, infections, reproductive issues, and higher mortality rates.

Therefore, it’s not enough to offer your fish the right-sized aquarium, clean water and food. Water temperature along with other water parameters are equally important.


While platy fish may be able to survive without a heater, they’ll most certainly won’t thrive without it, and it’s only a matter of time until health problems will start appearing because of the thermal stress you’re putting them through.

They may even seem fine for a while and you may think they’re thriving, but with several fish diseases symptoms already mean that it’s too late to salvage the situation.

Therefore, if you’re setting up an aquarium with platies and other tropical freshwater fish that require water in the same temperature range (e.g. mollies or guppies), make sure you invest in an aquarium heater.

There are various aquarium heaters available at various price points and you’ll be able to pick one that meets your budget, just make sure it’s sized accordingly and that it comes with a thermostat.

Featured Image:

Leave a Comment

Your email address will not be published. Required fields are marked *