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Love your molly fish, but you’re eager to keep other fish in your aquarium hoping to have a diverse fish tank that you can marvel at each day?

If you’re thinking about adding goldfish to your molly tank, I suggest you hold that thought while you read my article on whether you can keep molly fish and goldfish in the same aquarium.

A mixed-species fish tank is a delightful sight and a great way to observe the behavior of different types of fish.

Still, don’t go running to the pet store just yet. Not all freshwater fish can be kept in the same aquarium and this is true for goldfish and molly fish too.

molly-fish-goldfish

Therefore, if you were hoping to add some mollies to your goldfish aquarium, or vice versa, you’ll have to pick other mates, because these two are simply not a good match.

Molly fish and goldfish cannot be kept in the same aquarium because of their different water requirements and behavioral differences that make them incompatible.

For a better understanding of their incompatibility, let’s see exactly what their requirements are and what behavioral traits define molly fish and goldfish:

Molly Fish

Molly fish are a diverse species that enjoy spacious, well-planted tanks despite not being large fish. They’re active fish, however, so plenty of swimming space is crucial for them.

Mollies also enjoy being kept in groups, which is yet another reason to offer them a roomy tank. A 25-30-gallon tank is a suitable size for 4-6 molly fish.

As for their water parameters, molly fish aren’t too picky — water temperature should be in the 70°F to 82 °F range, water should be a bit hard with values around 15-30 dGH, while water pH should be around 7.0-8.0.

As you can see there’s lots of wiggle room in temperature and other water parameters for molly fish, however, they do enjoy stable water conditions without sudden changes or disruptions.

If kept in a species-only aquarium, some molly fish will enjoy a little aquarium salt in their water, something that other freshwater fish cannot tolerate.

It’s a misconception that all molly fish require salt in their water, it’s more like most molly fish can survive in brackish water if needed, but salt per se isn’t something mollies can’t live without.

Having said that, aquarium salt is often used to treat diseased mollies in quarantined aquariums.

Molly fish thrive on an omnivorous diet with brine shrimp, flake foods with high vegetable matter, tubifex, daphnia being staples in their diet.

Mollies enjoy plants in their tank not only for cover and shade but also because they like to nibble on algae that grows on plants.

You should be careful not to feed your mollies too much food (keep feeding to 2-3 times a day offering them small amounts each time), because they produce a lot of waste, which can cause water chemistry issues.

Goldfish

Goldfish are by far the most popular fish in home aquaria. They’re like a rite of passage for all aquarists, being one of the hardiest and beginner-friendliest fish around.

Goldfish thrive in colder waters that should be between 60° and 74° F, therefore, room temperature water is fine with them and a heater is not necessary. pH isn’t critical, but it’s best kept around 7.0-8.4, hardness should be up to 12 dgH.

Because these fish produce a lot of waste, an aquarium filter is indispensable along with live aquatic plants to further help keep the water clean. Weekly water changes at 25% are also advisable for goldfish aquariums.

As for their diet, goldfish are omnivorous, accepting a variety of foods. Feed them once or twice a day with food they can consume in 2-3 minutes.

Goldfish are peaceful and they should never be kept with fin-nippers and boisterous fish species.

Why You Shouldn’t Keep Molly Fish Together with Goldfish?

I strongly advise against keeping mollies and goldfish in the same aquarium. Here’s why:

  • Molly fish are quintessentially tropical, which means they enjoy warmer water than goldish will appreciate. Forcing one or the other to adapt to an extreme — even somewhat in their range — is not advisable as it will cause them undue stress that will eventually cause health problems;
  • Although both fish species are considered peaceful, many aquarists report that molly fish will bully goldfish when kept together, therefore, behavioral issues are also a strong argument against keeping molly fish in the same tank with goldfish.

Water conditions that don’t quite match the ideal requirements for your fish and stress caused by potential bullying will lead to your fish developing health problems, problems that you may not be able to prevent from progressing into something more serious.

Now that you know goldfish and molly fish aren’t a match, you should pick other mates that are compatible with your fish.

Fish Compatible with Mollies

Molly fish can be kept in the same aquarium with guppies, platies, swordtails, endlers, other mollies and peaceful livebearers, and even some invertebrates like shrimps and snails.

Fish Compatible with Goldfish

You can of course keep various types of goldfish together as well as other goldfish-compatible fish including rosy barbs, white cloud mountain minnows, rubbernose and bristlenose plecos, zebra danios, and tetras.

It’s best to keep goldfish with other goldfish in a species-only tank. This way you can ensure perfect water conditions and you don’t have to worry about bullying or fights.

Conclusion

Unfortunately, goldfish and molly fish should not be kept together and it’s best if you pick other, compatible mates that are more similar in water requirements and behavior.

Community tanks can be difficult to set up, but this shouldn’t keep you from finding compatible mates and enjoying a mixed-species tank.

Sure, you’ll need to do some research on the fish you intend to keep together and take behavioral aspects, tank conditions and water parameters into account.

With some research and dedication, you’ll be able to set up an aquarium in which your fish will feel comfortable and stress-free.

Written by Fabian

Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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