Can Molly Fish Live with Goldfish?

Last Updated on May 10, 2021 by cmoarz

Can Molly Fish Live with Goldfish?

If you are considering adding a molly fish to your aquarium, the answer is no. The main reason being that despite their similarity in appearance, they are incompatible tank mates. Mollies need warmer temperatures and goldfish require colder water. Another issue is that mollies can be aggressive towards other fish and will nip at goldfish for food.

Now, that’s not to say it’s completely impossible for a molly to be in an aquarium with goldfish. Some hobbyists will always find a way to meet the criteria both fish need to survive together.

However, that’s only for experienced aquarium hobbyists, as this will create a very high maintenance tank that most people wouldn’t be interested in anyway.

What are the reasons they don’t make good tank mates?

There are quite a few reasons mollies and goldfish can’t be tank mates. Mollies are tropical fish and need warmer temperatures, while goldfish are coldwater fish who require colder water to live comfortably – this is one of the reasons they’re incompatible tankmates.

Mollies need a constant temperature between 72 and 78 F, while goldfish on the other hand require a temperature between 65 and 75 F. Too much fluctuation in water temperature can cause the fish to become ill, so it’s not worth risking your molly’s well-being for the sake of having them live together with goldfish in an aquarium.

And although there is a bit of overlap in the temperatures, neither fish will truly be at peak health and performance if they are forced to both live in sub-part temperatures for their species.

Goldfish are pretty sturdy hearty fish and can probably survive (albeit not well) in this temperature mix, But mollies will surely suffer, get sick, and die as their immune system battled with the colder water temperatures.

Is there a way to incorporate both these fish in 1 tank comfortably? Yes, But it’s out of scope for this article. Perhaps it’s something we will write at a later date for those experienced in the hobby if there is interest. If you would like to read that, let us know in the comments or contact us!

Too continue:

Food is another issue when it comes to molly fish living with goldfish. Goldfish are super passive fish who will always wait for their next meal to come along. Mollies are not and usually end up eating most of the food in a tank before goldfish can get any.

Just because your goldfish is 2-3x the size of the molly doesn’t mean much when he’s not willing to use that size to his advantage.

Your poor goldfish could end up starving to death surrounded by food! How dreadful.

This is also bad for the molly, as it will become overfed and fat which will become very detrimental to its health.

All that extra food the molly stole has to go somewhere, and that brings us to waste issues:

Molly fish also produce more waste than goldfish (due to their active nature) which can lead to an ammonia spike and cloudy water, ickiness all around for both the mollies and the goldfish.

Both goldfish and Mollys are sensitive to ammonia spikes, and like many other creatures, will die or become sick very quickly. So not only is that an issue, it also increases the amount of tank maintenance one must do compared to if they lived individually or with tank mates that are compatible.


Mollies are aggressive fish that will nip at the fins of the goldfish, and chase them around.

Because goldfish are so passive compared to mollies they will likely tolerate a nip here or there which could end up being very bad for your goldfish.

A molly will go after the fins and scales of the goldfish, which will then cause the goldfish to be stressed out and become sick.

At the end of the day, the aggressiveness differences between these 2 species are enough to realize they should never cohabitate with each other. Passive fish should be with similar passive fish and aggressive fish should be with similar aggressive fish.

Tank size

in general, both species do well in a 20-gallon tank. But once you add them together that becomes a problem. You will need much much more space, at least a minimum of 40 gallons to keep them from being overly aggressive. And even then, you still have all the issues above to worry about.

How do you temperature control the same tank for radically different species? Is it possible? YES! but you can’t do it on a smaller tank! You need at least 40-gallons or more to even attempt to do such a thing.

Obviously, if you have no idea how that’s even possible, or if you only have a small tank at home, Just stop reading right here and go find another species of fish to cohabitate with your goldfish or molly. Please.


Owner of and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!