One of the key issues most pet owners have is getting the right fish for their tank. This is usually the result of having a certain size tank that can only accommodate certain types, sizes, and numbers of fish with the other issue being water temperature.
Different fish require different temperatures to be comfortable and thrive but when trying to combine different types of fish, it’s common to try and find a middle ground in terms of water temperature that all of your species can enjoy.
One question I see frequently is if mollies can live in cold water. It’s a reasonable question as goldfish (the most commonly owned fish) are coldwater fish and you might want to include some mollies in with them. We’ve even covered whether or not mollies can live with goldfish.
Whatever your reason, I’ll be covering whether or not mollies can live in cold water in this article and how you can make them more comfortable in your tank.
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Can Mollies Live in Cold Water
Different breeds of fish will thrive in different water temperatures ranging from cold water for coldwater fish to warm water for tropical fish. Some fish are hardy and actually have the ability to adapt to different water temperatures and not only survive, but also thrive.
Thriving is the keyword here, we don’t want our little swimmers to be barely surviving and living a poor quality of life. It’s our duty as fishkeepers to ensure their tank conditions give them the best quality of life possible and the ideal water temperature plays an important role in that.
With that said, can mollies live in cold water?
Mollies are hardy fish and can live and survive in cold water but this isn’t their ideal environment. Mollies are best adapted to living in temperatures of 72 – 82 degrees Fahrenheit. They don’t need a heater if they are kept in a warmer room but, in general, you should avoid keeping them in cold water.
This point hopefully sums up what I’ve covered so far. A mollie can live in colder water and will survive, much like a human can withstand cold if they have to but looking at the perspective of both, we definitely prefer it to be warmer in our homes.
For the rest of this article, I’ll cover what the ideal tank requirements are for mollies and discuss how and when they could be kept in cold water but again, this wouldn’t be my recommendation!
What Temperature Can Mollies Live In
First, it’s worth pointing out that mollies need a stable temperature more than they need a defined temperature.
What I mean but this is that sudden and drastic changes to the water temperature will shock and stress out the mollies and affect their immune system making them susceptible to illness, infection, and potential death.
This isn’t an uncommon occurrence either, vets at Pet Coach say that temperature can be the most important environmental factor for your fish and any sort of a sudden or significant change in the temperature will significantly impact their immune system and health.
Therefore, before you even consider the water temperature that you’ll keep your mollies in, you’ll need to make sure it will stay constant. This could mean if you live in a cold area you’ll need to use a tank heater (which I’ll come on to shortly) and if you live in an overly hot environment, you’ll need a chiller (less relevant for this article).
Mollies can live comfortably in temperatures ranging from 72 – 82 degrees Fahrenheit, with this video below demonstrating that 75 – 80 degrees Fahrenheit might be best.
This temperature range is the best for your mollies to be comfortable and to thrive. The Aquarium Guide states that mollies also need warmer water to breed successfully and studies have also shown that mollies breeding in warmer temperatures produce more fry that is also healthier.
It’s even suggested that during breeding, you should raise the temperature in your tank by a few degrees (nothing drastic and not more than their comfortable range) to make them more comfortable during breeding.
This point alone should be enough to encourage you to think against keeping your mollies in cold water!
Mollies breeding in cold water, by comparison, are observed to breed far fewer fry and this is another important point to take into consideration if you wanted to keep mollies and breed them in colder temperatures.
FAQ
Below are some of the frequently asked questions that I come across when it comes to keeping mollies in cold water. As they are such popular and frequent questions, each one justified having its own specific section.
Can Mollies Live in a Pond
Whether or not mollies can live in a pond will depend entirely upon your geographical location. In certain parts of America like Minnesota, North/South Dakota, or Alaska for example, temperatures are often low even in the summer, and therefore it is far less likely that mollies can survive in these temperatures unless you use a pond heater.
In warmer climates though, it can definitely be possible for mollies to live in a pond. Provided they get enough food and the water quality is as good as what you would keep in a tank, there is no reason why a molly can’t live in a pond in areas with warmer climates (and no drastic drops in temperature).
This person even went as far as saying the pond was “overrun” with mollies which clearly shows that they can survive and potentially even thrive in a pond if the conditions are favorable.
The Spruce Pets also list mollies as fish that could survive in an outside pond but again, they make the strong case that the living conditions need to be favorable and cite sudden temperature drops as an issue in particular.
This short video below also shows mollies living happily in a pond so as long as you live in an area with a favorable climate, they should be fine.
Should Mollies Live in Cold Water
Mollies can live in cold water but this is more for survival and when keeping mollies as pets, you should not keep them in cold water. Just because they can survive in cold water does not mean that they should!
An ideal temperature for your mollies is 75 – 80 degrees Fahrenheit and this is going to be the same regardless of what breed you keep. Mollies are tropical, warm water fish and just because they are hardy and can handle the cold does not mean that they should have to.
It’s also worth pointing out that older mollies are better capable of surviving in colder temperatures but young fry and mollies <2 years old will struggle much more in cold water and really need warmer temperatures to survive.
This ties in with the research from earlier that shows mollies will breed more in warmer water than colder water as the young will have a better chance of survival.
Do Mollies Need a Water Heater or Chiller
While mollies can survive in a range of different water temperatures, I mentioned earlier that they are incredibly susceptible to sudden and/or drastic changes in water temperature.
This means that if you do not keep something in the tank to regulate water temperature then you are putting them at risk from external temperature changes outside of their tank.
While mollies do not need a heater (or chiller for incredibly warm and humid climates or rooms), it would be advised to keep one as this will help to maintain and regulate the temperature of their water keeping them comfortable and happy.
If for example, you do not keep a heater in the tank and the outside temperature drops from 80 degrees Fahrenheit to sub 60 degrees overnight, this will significantly impact the water temperature in the tank and could be fatal to your mollies.
A heater will therefore protect your fish against sudden temperature drops and if you are experiencing sudden temperature rises, you should gradually decrease the temperature of your tank’s heater by 1 – 2 degrees to again help reduce any impact on your fish from external temperature swings.
In Summary
Mollies are quite hardy and adaptable fish which is always a good thing when it comes to water temperature. Some fish have a very narrow range in terms of temperatures that they can live in so thankfully, mollies can live in a wide range of temperatures.
While mollies can live in cold water, this doesn’t mean that they should. Mollies thrive best in temperatures of 75 – 80 degrees Fahrenheit so this is the temperature you should look to keep them in.
Also, remember that any sudden changes can lead to your mollies immune system becoming affected which can then lead to illness and infection so make sure you are frequently monitoring the temperature of the water taking into consideration temperatures outside of the tank.
