What Temperature Do Mollies Like?

Mollies are freshwater fish that belong to the Poeciliidae family. They originate from a tropical climate, which means mollies survive best in warm water temperatures that range between 70 to 82 degrees Fahrenheit.

While mollies are adaptable fish that can survive in varying water temperatures and conditions, they must exist in their preferable temperatures so they can lead a healthy and full life.

In this post, we discuss the ideal temperature range for mollies and how you can maintain it in your tank, so stick around.

What Temperature Do Mollies Like?

Molly fish like to live in warm water temperatures ranging between 70-82 degrees Fahrenheit. If the water gets colder or hotter than ideal, health, growth, behavioral, and bacterial issues might arise.

Luckily, there are several ways through which you can ensure that the water temperature in your tank remains within the ideal range so that your mollies can live happily and healthily.

Balloon Molly Fish

What Is the Lowest Water Temperature Ideal for Mollies?

Mollies are tropical freshwater fish, so they prefer to live in waters of warm temperatures. The minimum water temperature that mollies prefer is 70 degrees Fahrenheit.

While mollies are tough fish that can adjust themselves and still survive at temperatures below their recommended 70F, keeping them in their ideal water warmth is needed for their flourishing and wellbeing.

What Happens When Water Temperature Gets Lower Than Ideal?

Mollies living in water temperatures less than their ideal 70F could be at risk of several issues, including:

Growth Issues

In water temperatures colder than ideal, mollies usually stop growing. You will notice that your mollies remain relatively small in size and don’t reach their full growth potential of 3-4 inches.

Health Issues

If the water temperature becomes colder than ideal, mollies’ immune systems suffer, making them more likely to suffer from diseases or parasites.

Mollies’ metabolism levels could also get extremely low because of colder than usual water temperatures, which negatively affects the fish’s health and puts them at risk of illnesses.

Behavioral Issues

Low water temperature affects not only mollies’ health, but their behavior, too. Mollies will start to become lazy and dull as it gets colder, causing them to stop swimming and interacting and instead isolate themselves in hiding spots.

Colder than ideal water will also put mollies under a lot of stress, causing them to become aggressive and fight one another.

The fish will also experience a loss in appetite, causing them to eat less, which might end up shortening their lives.

Reproduction Issues

As the fish becomes too cold, all their energy goes towards either trying to look for a warmer place or keeping themselves warm, which hinders their ability to reproduce.

How to Prevent Water Temperature From Getting Lower Than Ideal?

There are quite a few useful tools that can help you keep the tank warm enough and ensure that mollies live in their ideal water temperature.

Two of the most effective tools are:

Aquarium Heater

You can use an aquarium heater to prevent the aquarium temperature from dropping below the ideal temperature required for your mollies.

The aquarium heater is set to a limit that shows how high the water temperature should be, or the limit it should reach, in other words.

If the water temperature fluctuates, the heater will automatically set the water temperature to the level that was predetermined.

By using an aquarium heater, you can ensure that the mollies find the water to their preferred temperature and never below it.

Aquarium Thermometer

Using an aquarium thermometer can also be an excellent tool to help maintain an ideal water temperature in the tank. An aquarium thermometer identifies the exact current temperature of the aquarium water.

The thermometer can also be set to a desired specific temperature and will immediately notify you in case of a temperature change.

What Is the Highest Water Temperature Ideal for Mollies?

You might think that by maintaining the minimum temperature for mollies that everything is set. However, a water temperature higher than ideal can also cause lots of issues to your mollies.

80 degrees Fahrenheit is the maximum temperature at which mollies can live healthily. Mollies can endure water temperatures up to 82F, but they will still need to forcefully adjust and settle themselves in this temperature, which is why it’s not recommended.

What Happens When Water Temperature Gets Higher Than Ideal?

While mollies are tropical fish that prefer warm water, there’s still such a thing as too hot when it comes to the water temperature ideal for their survival.

Water temperature above 80F can cause several issues for mollies, including:

Bacterial Issues

As the water temperature in the aquarium rises above the ideal level, it negatively affects the useful bacteria living in the fish habitat that plays a key role in the biological filtration and the nitrogen cycle.

This leads to the buildup of ammonia, which causes many other bacterial problems that affect the life of mollies.

Black Molly Fish

Oxygen Issues

Water temperature above 89.6 degrees Fahrenheit causes the level of oxygen in the water to decrease. This increases the risk of suffocation in the tank.

Stress Issues

Same as it is with cold water, a higher than ideal water temperature can cause stress to mollies.

Mollies tend to flee places with very warm water in nature, which they cannot do in an aquarium, which causes them stress and affects their health and wellbeing.

With the lack of oxygen, too, mollies become frantic and move a lot, making the situation much worse and increasing the risk of suffocation even more.

Behavioral Issues

Just like it is with cold water, high water temperature causes mollies to become more stressed and aggressive towards other tank mates and themselves.

They will also start to become lazy, as opposed to their energetic nature.

How to Prevent Water Temperature From Getting Higher Than Ideal?

To prevent the water temperature from getting higher than ideal and to ensure suitable living conditions for mollies, you can use:

Aquarium Chiller

An aquarium chiller is a nifty device used to cool down water temperatures that are too high in fish tanks and aquariums.

The device works by moving compressed gas into the radiator, where a fan blows it out into the tank water to cool it down. The aquarium chiller has a control unit that you can set to the desired water temperature.

The control unit observes the temperature and turns the cooling system on automatically when the water needs cooling, then turns it off when it reaches the desired temperature.

Bottom Line

While mollies are adaptable freshwater fish as far as where they can survive, they can still face many issues if the water temperature isn’t within their comfortable temperature range.

Mollies prefer to live in warm water with a temperature between 70 to 80 degrees Fahrenheit. If you’re planning to raise mollies, you may need either aquarium heaters or chillers to ensure the right temperature for the fish to thrive and flourish.