Skip to Content

Can You Keep Mollies And Goldfish In The Same Tank?

Goldfish are the most commonly kept species of fish in the world and the vast majority of people who do get involved in the fish keeping hobby tend to start with goldfish as their first species of choice.

From there, people tend to start to build up their own community tanks by adding additional species of fish to the tank with their goldfish.

We commonly see people reaching out to ask different questions about various tank mates for goldfish but more recently, there has been a large number of people asking about keeping mollies and goldfish in the same tank as each other.

Due to so many people asking about keeping mollies and goldfish together, we wanted to publish this dedicated article going over the topic to try and help as many of our readers as possible.

Can I Put Mollies With Goldfish?

Although the majority of experienced fish keepers will advice beginners not to keep mollies and goldfish in the same tank as each other, it can be done if the tank setup if perfect and a number of people do keep mollies and goldfish together without issue.

The trick is to plan out the aquarium setup in advance so you are able to optimise the tank around the needs and requirements of your goldfish and mollies.

We are going to cover everything that you have to factor in below in our article to try and help you setup the perfect molly and goldfish tank but there are some areas where having experience with maintaining steady, consistent water parameters is essential so having prior experience with fish keeping is ideal.


One of the most important things to consider when adding new fish to your tank, especially when keeping mollies and goldfish together, is the temperament of the fish.

Mollies are a particularly active and playful species of fish and they can be quite boisterous in a tank setting, often swimming around quickly and playing with other fish in the tank.

This is generally fine with goldfish as they are relatively laid back fish but there are some cases where mollies can be a little too much for goldfish and this can cause stress which leads to health issues further down the line.

The Temperament Of Mollies!

Mollies are a species of fish which have been known to be quite peaceful and easy to keep with other fish in the aquarium.

They are not an aggressive fish by nature and they will often get along well with other fish in the tank, including goldfish in some tank setups.

The only time that you may have issues with mollies is if you have a particularly active or playful molly which can sometimes be too much for goldfish, especially younger goldfish or fry.

In smaller tanks mollies may show some aggression to goldfish, especially if the molllies are stressed, ready to breed or pregnant.

The Temperament Of Goldfish!

Goldfish are a very popular species of fish to keep in the home aquarium and they are well known for being very peaceful, easy to care for fish.

They are not an aggressive species of fish and they will often get along well with other fish in the tank.

Even though some species of goldfish are larger than their tank mates when fully grown, they are still peaceful and placid.

Can The Temperament Of Mollies And Goldfish Worth Together?

The temperament of mollies and goldfish can work well together if the tank is setup correctly and the fish are healthy and happy.

As we mentioned above, any problems that you have with a tank will come from the mollies, not the goldfish but if you offer your mollies plenty of space and a stress free envrionment with optimal water parameters with plenty of hiding places, they are usually fine with goldfish.


One of the most important things to consider when adding new fish to your tank, especially when keeping mollies and goldfish together, is the diet of the fish.

Not only do you need there to be plenty of crossover in the diet so you can just use one product but you also want something to meet the nutritional needs of your fish.

In addition to that, you also want something that is easy to use as overfeeding or left over food is very common for beginner fish keepers and this will cause you issues later in your jourey.

The Molly Diet!

Mollies are omnivores which means that they will eat both plant and animal matter.

In the wild, they will often graze on algae and other plant life but they will also eat small invertebrates, crustaceans and fish fry.

It is important to offer your mollies a varied diet in the aquarium so they can get all of the nutrients that they need to stay healthy.

A good quality flake food or pellet will give them the majority of the nutrients that they need but you should also supplement their diet with live, frozen or freeze dried foods.

Bloodworms, brine shrimp and daphnia are all good choices for mollies and they will help to keep them healthy.

The Goldfish Diet!

Goldfish are also omnivores but are far less picky when it comes to their food than mollies.

They will eat pretty much anything that you offer them but it is important to offer them a diet that is high in plant matter.

Goldfish are grazing fish which means that they spend most of their time looking for food.

This means that they will wonder around their tank foraging and may end up getting into terratory that your mollies feel is their during the breeding season potentially causing some fin nipping.

Is There Enough Crossover In The Diet Of Mollies And Goldfish?

Due to goldfish and mollies both being omnivores, there is plenty of cross over in their diet to keep both species of fish in the same tank as each other without having problems with food.

A decent flake or pellet food should be ideal for the bulk of their daily calories.

Bloodworms, brine shrimp and daphnia are all excellent treat food options for both goldfish and mollies with the live, frozen, and freeze dried variants all being suitable too.

Tank Size

A larger fish tank is always better than a smaller one. Not only does it provide more space for your fish, but it also helps to maintain water quality by distributing the load more evenly.

When stocking a larger tank, it is important to be mindful of the size of the fish and how many you can comfortably fit in the tank without overstocking it.

Overstocking a tank can lead to water quality issues and stress for the fish which can then lead to disease.

The rule of thumb when stocking a fish tank is 1-inch of fish per gallon of water but this is only a guideline and you should always consult with a professional before adding new fish to your tank.

Molly Tank Size Requirements!

Although mollies can technically do well in a tank that is only 10 gallons in size, it is best to provide them with a little more room to swim.

A 20 gallon tank should be the minimum size for mollies as it allows you to keep a number of mollies in the tank with minimal issues.

When looking to keep mollies with other fish species, you usally have to increase the tank size by a minimum of 10 gallons.

Goldfish Tank Size Requirements!

The tank size requirements for goldfish will depend on the exact species of goldfish you have as there are over 30 different types of goldfish but thankfully the majority of them are small when fully grown.

Most species of goldfish will be fine in a 20 gallon tank but this will depend on the number of goldfish that you want to keep in the tank.

What Size Tank Do I Need For Mollies And Goldfish?

We would usually recommend an aquarium tank that is at least 30 gallons in size for your goldfish and mollies to live in to make sure that the tank has plenty of space available for your fish.

You should try to avoid overstocking it too as this can stress your mollies and cause them to be more aggressive.

If you have the space and budget available then a 40 gallon tank or larger will be much better as it allows you to take advantage of some of the tips and tricks for keeping mollies and goldfish together that we will share in our habitat section later in the article.

Water Parameters

Water parameters are important to keeping your fish healthy as they help to regulate things like pH levels, ammonia levels and nitrate levels.

If any of these water parameters get out of balance, it can lead to health problems for your fish and can even lead to death.

It is therefore important to test your water parameters on a regular basis and to take action if any of the levels get out of balance.

Poor water parameters will stress your fish out and make it more likley for your mollies to chase and nip their tank mates.

What Water Parameters Do Molliles Need?

Mollies are a tropical fish species so they require warm water to live in with a temperature range of 70-82 degrees Fahrenheit being ideal.

The pH level should be between 7 and 8 and the hardness should be between 15-30 dGH.

What Water Parameters Do Goldfish Need?

The water parameters that goldfish need are a little different from mollies.

The ideal temperature range for goldfish is 60-74 degrees Fahrenheit with a pH level of 7-8.4 being ideal.

The hardness of the water should be around 12 dGH for goldfish.

What Water Parameters Should A Tank For Mollies And Goldfish Have?

When setting up a molly and goldfish tank, we would recommend that you priortotise the water parameters for your mollies.

Not only are goldfish generally more hardy than mollies but poor water parameters for mollies can stress them and make them aggressive.

As you can see, both species of fish do have some cross over in their required water temperature so aiming for a 70-74 degrees Fahrenheit regular temperature can keep both species happy.

There is also some cross over in the pH requirements of the fish too and you can usually go for the slightly higher gGH levels that the mollies require without the goldfish having any real problems.


Live plants and fish hides are important in a tank for mollies and goldfish as they provide the fish with a place to hide from each other.

Mollies will often hide in plants to escape from the attention of goldfish, and vice versa.

A fish hide is also a great place for your fish to hide if they are feeling stressed or need a break from each other.

You should try to have at least one fish hide and some live plants in your tank for mollies and goldfish.

Live plants also offer a number of benefits for your water parameters as they help to keep the water clean and oxygenated.

Molly Habitat!

Mollies love to hide and they will commonly hide for a couple of hours each day to relax.

This is a benefit for you if you are keeping mollies with goldfish as it helps to destress your mollies and prevent them from becoming aggressive so we would always recommend you have live or fake plants in your molly and gold fish tank.

Goldfish Habitat!

Goldfish tend to be more focused on grazing on the algae growing on the plants rather than hiding but in some situations, the goldfish may get amongst the plants or in a fish hide to relax and feel safe.

What Habitat Should I Use For Mollies And Goldfish?

We would recommend using a combination of live plants and fish hides in your molly and goldfish tank to provide the fish with the best possible habitat.

You can use either real or fake plants as both will offer your fish somewhere to hide.

It is important to have a good mixture of plant types in your tank as this will provide different levels of hiding places for your fish.

You should also have at least one fish hide in your tank for mollies and goldfish as this will provide the fish with a place to go if they are feeling stressed or need a break from each other.

The fish hide can be anything from a cave to a piece of driftwood and it is important to make sure that it is big enough for both your mollies and goldfish to fit into.

How Often Does Tank Maintenance Need To Be Done For A Molly And Goldfish Tank?

Tank maintenance for a molly and goldfish tank should be done on a weekly basis.

You will need to do a partial water change of around 20-30% and clean the filter.

It is also a good idea to vacuum the gravel to remove any uneaten food or waste.

We know that people live busy lives these days and may not be able to do tank maintinance weekly so you can do it eery two weeks but we would not recommend intervals longer than this as it becomes more likley that your mollies will be stressed as their water parameters get bad.


That brings out article going over keeping mollies and goldfish in the same tank as each other to an end.

Although it is challanging and often discouraged, you are able to keep mollies and goldfish in the same tank as each other if you really want to but we wouldent usually recommend that you do it if you are a beginner fish keeper.