Can Platies Live in Cold Water?

Platies are bright-colored freshwater aquarium fish that are easy to care for and maintain. Still, there’s a common question often asked by aquarists: can platies live in cold water? The quick answer is: no.

In general, there’s a shared belief that platies are cold water fish. Yet, that’s not necessarily true.

These tropical species thrive within tolerable temperatures, even without a heater. Their one stipulation is that tank conditions remain steady and constant.

If you’re interested in finding out more about platies and their living conditions, we’ve got more to cover. So, let’s get started.

Can Platies Live in Cold Water?

Classifying platies as a cold-water fish is one of those misconceptions that has infiltrated the world of freshwater aquariums. Yet, it’s safe to say that platies can’t live in cold water, nor can they be considered cold-water fish.

Nevertheless, before we can say without a doubt whether platies are cold-water fish or not, we have to first understand what it means for a fish to be classified as such.

However, there’s a slight snag: there are three ways you can define ‘cold-water’ fish, depending on the context.

For example, if you’re talking about aquarium fish, this term refers to the fish species capable of thriving without a heater. So, then, in this context, platies are definitely cold-water fish, as long as temperatures remain within a consistent range.

Another example of cold-water fish species is those that can thrive in outdoor ponds, such as koi and Golden Rainbow Trout. These species can survive at temperatures as low as 50°F, which isn’t something platies are fond of.

The third category is when anglers categorize fish species into warm-water or cold-water. Anglers recognized that certain species become more active in cold water temperatures, such as trout, burbot, and salmon—hence the name. No, platies don’t belong to this group either.

School of Neon Blue Platies

What Is the Ideal Water Temperature for Platies?

Like many other fish species, platies (Xiphophorus maculatus) are poikilothermic, which is just a fancy word that means ‘cold-blooded.’

This means that their body temperatures adapt to their surroundings. Moreover, their core temperatures can either fluctuate slightly higher or lower than their ambient environment.

So, then why do different fish species need different water parameters? Well, this depends on several factors, including their metabolic rate, tank size, and water quality.

Yet, keep in mind that platies are tropical fish that like their water temperatures to be between a fair 75°F and a balmy 80°F. This isn’t exactly what you’d consider ‘cold water.’

Do Platies Need a Heater?

Whether or not you need a heater for your platies depends on how warm your room temperature is. In cold regions, you definitely need to add a heater to the tank to ensure that the tank water remains anywhere between 75°F to 80°F, as mentioned above.

If you live somewhere warm, you can forgo the heater entirely. In fact, they’re probably better off without it because too much heat might cause more harm than good.

So, to ensure temperatures remain steady, we recommend that you invest in a reliable tank thermometer and check the water every day. If temperatures drop more than five degrees below 75°F, it’s time to add a heater.

Choosing a heater depends on the amount of water volume in the tank. The general rule is that the wattage should range between 2.5 and 5 watts per gallon of water.

How to Maintain Water Temperatures without a Heater

Many aquarists prefer to keep their tank organic and naturally balanced. So, they opt not to install a heater.

Instead, they look for other ways to keep the water warm and comfortable for their platies.

Direct Sunlight

Does your home get direct sunlight from a balcony or window? Then, why not place the tank there for a couple of hours and let the water soak in all that natural warmth.

You’ll save energy and lower your electricity bills. Best of all, platies aren’t light-sensitive, which means they enjoy basking in natural sunlight.

Artificial Heat Source

If you don’t get any sunlight, try putting the tank near a fireplace or warm oven. You can also install a lighting system, which will keep the tank nice and toasty, as well as make it brighter. The warmth from these heat sources will keep the water nice and toasty, which the platies love.

Whichever choice you go with, remember to check the temperature every half hour or so. The water can warm up pretty quickly, and you don’t want your platies suffering from high temperatures.

Tank Insulation

Another basic way to maintain ideal temperatures is to use insulating materials. They’re easy, quick, and efficient. Plus, they do an excellent job of warming up the tank, especially if you live in cold regions.

The problem with insulation is that it reduces the amount of light going into the tank. Insulation also doesn’t make for an aesthetically pleasing aquarium.

Common tank insulators include:

  • Styrofoam
  • Newspapers
  • Blankets
  • Towels
By Marrabbio2 [CC BY-SA 3.0]

What Happens to Platies in Cold Water?

We now know that platies aren’t able to regulate their body temperatures. That’s why they rely on their surroundings to be just right for their survival.

Still, they’re tough enough to adapt to temperatures that are a few degrees below their ideal 75°F, but not for long.

Also, if temperatures drop more than four degrees, it can have an adverse effect on their survival.

For starters, it prevents them from carrying out their normal, everyday metabolic activities, such as catabolism and anabolism.

Catabolism is when fish break down metabolites to generate energy. Alternatively, anabolism is how fish use this produced energy to maintain their growth, reproduction, and overall health.

If platies can’t carry out these two processes, they can become severely sick and even die.

Here are some problems that can face platies if water temperatures are too cold:

  • Stress
  • Stunted growth
  • Reduced energy levels
  • Breeding problems
  • Diseases


To sum up, can platies live in cold water? No. in fact, it can cause the fish to suffer, increase their stress levels, and even result in their death.

Platies prefer moderate temperatures to boost their health and development.

The good news is that there are several ways of maintaining ideal temperatures. As long as water temperatures remain in that ideal range that platies love so much, everything should be fine.