Do Platies Need a Heater?

Yes, platy fish need an aquarium heater to help regulate the temperature in their tank. Platies are tropical fish that thrive in water temperatures between 72 and 78 degrees Fahrenheit. Temperatures outside of this range can cause stress, illness, or even death of your platies. 

Keep reading to find out why platies need a heater, what kind of heater you should buy for your platy fish, and how to keep your platies warm if the power goes out.

Why do platies need a heater?

Platy fish originated in Mexico and Central America, where the water temperatures are warm year-round. Aquarium-kept platies are happiest when their living environment closely matches that of platy fish in the wild, so to give them the best life possible, their water temperature should be as close to 72-78 degrees Fahrenheit as possible.

Arguments against tank heaters for platy fish claim that platies were successfully raised for decades without tank heaters before they became popular. Though raising platy fish without a heater may technically be possible, there are drawbacks to keep in mind.

Platy with Black Face Swimming

Keeping a proper water temperature

To keep platy fish alive, the water in the tank must stay within a precise temperature range. If the temperature in the tank is slightly below 72 degrees Fahrenheit or slightly above 78 degrees Fahrenheit, platy fish will be okay, though they may become stressed or ill. However, major temperature swings are a death sentence for these tropical fish.

Water temperatures rise and fall slower than air temperatures, so even if the temperature in your house is 75 degrees Fahrenheit, the water temperature in the tank may be lower. This means that keeping platy fish without a tank heater may require keeping your home at uncomfortably warm temperatures.

Potentially shorter lifespans

Even if your platy fish adjust to a slightly cooler or warmer water temperature than is ideal, their health may suffer. Living in an environment that is unnatural will cause your platy fish undue stress, meaning they may be more susceptible to illness and death.

Imagine yourself living through a frigid winter with limited heat: you may survive, but the stress will weaken your immune system and deteriorate your strength. Platy fish kept in unnaturally cool water temperatures experience the same thing. Providing your platies with a warm, constant water temperature will help them have longer, healthier lives.

What size heater do I need for my tank?

If you decide to use a heater in your aquarium to keep your platy fish happy, you want to have the right size of heater for your tank. That way, you will be able to keep a constant, healthy water temperature for your platies.

The size of heater you need for your aquarium depends on the size of your tank. To find out the size of heater you need, multiply the gallons in your tank by 5.

For example, if you have a 10-gallon aquarium, multiplying 10 x 5 = 50, so you need a 50 watt heater for a 10-gallon tank. Use this same formula for whatever size tank you have.

Be sure to have an extra aquarium heater on hand in case your main heater malfunctions. If your heater stops working and you don’t have another to replace it with, the water temperature in your tank will drop, potentially harming your platy fish.

It’s also important to note that it’s necessary to have a thermometer in your aquarium. Most tank heaters have thermometers that allow you to choose the correct water temperature for your fish, but keeping a separate thermometer in the tank will help make sure your heater is functioning properly and keeping the water at the right temperature.

How do I keep my tank warm during a power outage?

Because platy fish need a consistent water temperature, losing power can be a big concern during winter months in places that get below 68 degrees Fahrenheit. Thankfully, you have a few options to help keep your tank as warm as possible if a power outage strikes.

Use a generator

The best possible solution for keeping your water warm in a power outage is to use a generator. If you’re lucky enough to have one on hand, you won’t have to worry about a drop in water temperature as long as the generator is running.

Heat the room with a fireplace

Another relatively simple solution is to use a fireplace to heat the room your aquarium is in. Of course, this only works if you have a wood-burning or gas fireplace, but it’s an easy way to keep your platy fish as comfortable as possible during a power outage.

Keep in as much heat as possible

If you don’t have a generator or a fireplace, you can still help slow heat loss from your aquarium. Make sure to close the lid on the tank, and then wrap it with towels to help keep in as much heat as possible.

This method won’t keep the tank warm forever, but it’s a better alternative than leaving your tank open for heat to escape freely. Hopefully, the power will come back on quickly, keeping your platy fish warm and safe.


Platy fish are resilient, but they are tropical fish who need warm water temperatures to survive. They thrive in water temperatures ranging from 72 to 78 degrees Fahrenheit, so if you live somewhere the temperature drops in the winter months, a tank heater is the best way to give your platy fish the best possible life.

To keep your tank warm year-round, make sure you have the right size of heater, along with a thermometer. Regularly checking the temperature of your tank is an easy way to make sure your platy fish stay comfortable.

Platy fish who are warm and safe live long, happy lives and breed regularly. Taking the necessary steps to keep the right water temperature in your tank can not only help your platies live as long as possible, but will also provide you with plenty of platy fry for years to come.