Do Mollies Need a Heater? Time to Find Out!

As a first-time molly keeper, the question of whether or not these little beings need a heater might be circling your thoughts. Well, the answer is yes, mollies should live in an aquarium with a heater because they’re tropical fish; so they like their water a notch warm.

In this article, we’ll discuss everything related to the ideal temperature for mollies so that your fish are always happy and healthy. “Do mollies need a heater?” You’ve asked, and now it’s our turn to answer your question in-depth.

Let’s dive right in!

Do Mollies Need a Heater If I Live Somewhere With a Warm Climate?

It’s not enough for your region’s general climate to be warm to put your mollies in a fish tank without a heater. To be 100% safe, you must be living in a place where the weather is considered tropical so that your fish won’t face unexpected bursts of cold.

Even if the climate where you’re staying is positively hot all year round, there’s still the possibility of a chilly night or a cold morning.

The thing about a heater is that it keeps the tank’s temperature steady no matter what time of the day or month of the year it is. So, you’ll be more assured that your fish are living in an ideal environment 24/7.

Black and Yellow Molly Fish

What Temperature Do Mollies Prefer, and Why Must It Be Stable?

Mollies should be kept at 75 to 85 degrees Fahrenheit to mimic the climate of their tropical habitats. This range of temperature is easy to provide for your fish by installing a good tank heating system.

The reason why it’s important to maintain a steady water temperature is that mollies can become sick if exposed to sudden periods of cold weather.

See, a decrease in temperature gives the opportunity to germs and other harmful creatures to make the fish tank their home. As their numbers grow bigger in the water where your fish live, your mollies could soon fall prey to these parasites.

Can Mollies Survive in Cold Water?

According to experts, mollies are pretty tough despite their cute appearance. It won’t be the optimum environment for them to live in, but mollies can stay in slightly colder water for a while.

For example, you could leave your fish in an unheated tank for a few days until you get your heating system installed. It’s the sudden change from high to low temperatures that could make them ill.

If you ever need to change temperatures from cold to warm or vice versa, make sure it’s gradual so that your fish’s tiny bodies can adjust with no trouble.

Also, bear in mind that keeping your mollies in cold water for a long period of time can have negative effects on their health. These little buddies could end up with growth difficulties, weaker immune systems, diseases, and trouble with giving birth.

The bottom line is that mollies can definitely survive in cold water, only if it’s for a short amount of time. But they won’t thrive in such low temperatures.

When Is It Too Cold Or Too Warm for Mollies?

Slightly colder water, say 70 to 75 degrees, should be okay for mollies to live in. But again, it’s not perfect. Anything below 70 degrees is considered too cold and might harm your fish’s health quite rapidly.

As for when it’s too warm, it’s usually around 85 to 90 degrees when mollies might be uncomfortable. Keep in mind that, just like being in too cold water, exposure to too much heat may cause stress, which you don’t want your fish to face.

Plus, an increased temperature kills the good bacteria in the water, which might ultimately lead to a buildup of ammonia. No one wants that!

How Can I Tell If the Water in the Fish Tank Is Too Cold?

Thankfully, the behavior of your mollies can tell you a lot about whether or not the water temperature is okay for them to stay in.

If it’s too cold for their comfort, your mollies will usually start showing these signs:

  • A decrease in activity (looking sleepy and sluggish)
  • No movement at all

Sailfin Molly

How Can I Tell If the Water in the Fish Tank Is Too Warm?

Again, your fish will let you know if the temperature you’ve set the heater to isn’t working with their little bodies.

Look for these symptoms that the water is too hot for your mollies to live comfortably in:

  • An increase in activity (swimming fast around the tank)
  • Racing to the surface to gasp for air
  • A loss of appetite
  • Hiding or looking for places to hide
  • The tendency to rest at the bottom of the tank

What Are Some Ways to Keep the Tank Warm Until I Get a Heater?

Shopping for a heater in a day or two but don’t want your mollies to stay in cold water? Well, here are a few things you could do to make their environment warmer for the time being:

  • Start by using a thermometer to keep a close eye on the water temperature
  • Add strong light sources to the corners of the tank
  • Cover the tank with a lid
  • Wrap a few blankets around the aquarium
  • Turn up the heat in your place and move the tank to the warmest room in your house

It’s best not to consider adding warm water to the tank as an option here since mollies are sensitive and they might not adjust easily to the change.

To Wrap It Up

Do mollies need a heater?

Yes, mollies require a tank heater because their bodies are designed for living in tropical conditions. A heater will ensure that the water temperature remains warm enough for your little guys to have a healthy life inside the aquarium and keep sudden bursts of cold at bay.

Remember to adjust the heater to 75 to 85 degrees Fahrenheit to suit your mollies’ needs. But if the temperature is slightly higher or lower, there’s nothing to worry about.