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The Ultimate Swordtail Molly Care Guide!

There has been a massive influx of new people to fish keeping over the last few years and the spike in popularity of the hobby has also resulted in a huge spike in the number of people reaching out with a wide range of questions about various fish.

Without a doubt, one of the most popular fish that we see people reaching out about month in and month out are mollies.

They are easy to keep, beginner-friendly, and are generally a low maintenance fish for the most part so it’s not surprising that so many people new to fish keeping are starting off with some mollies.

Due to a number of social media groups, we have noticed more and more people referring to “swordtails” as “swordtail mollies” and although they are from the same family, swordtails and mollies are actually from a different genus and are different types of fish.

Still, we constantly see people asking questions about the swordtail molly when they usually just mean swordtails and due to this trend only becoming more popular, we will be sticking the the “swordtail molly” term for most of this article.

We also see a number of people reaching out about making a swordtail molly hybrid fish too and initially though that was what a swordtail molly would be but we will cover this in more detail later in the article.

Are Swordtails The Same As Mollies?

Swordtails are not the same as mollies with swordtails being from the Xiphophorus genus and mollies being from the Poecilia genus.

Both swordtails and mollies are from the same family of fish known as Poeciliidae though so we can see where to confusion comes from as they do have a number of similarities.

The photograph above offers an excellent example of why beginners to fish keeping can easily get confused as you can see the similarities between the swordtail in the foreground and the molly in the background of the photograph.

Depending on the color and pattern of your fish, they can end up looking very similar to each other while having a large number of similarities between the two but this is very common for most of the fish in the Poeciliidae family of fish.

We think that this is where the term “swordtail molly” originally came from due to a number of beginner fishkeepers on social media confusing swordtails and mollies with each other and the new term becoming popular.

Due to social media being so popular now with so many people being on there, we have seen a number of inaccuracies about fish keeping quickly becoming accepted at a worryingly fast pace.

“swordtail and molly” by Genista is licensed with CC BY-SA 2.0. To view a copy of this license, visit

Can Swordtails And Mollies Interbreed?

Swordtails and mollies are not able to interbreed due to being from different genus’ within the same family of fish.

This means that they do not have the correct number of chromosomes to breed with each other and produce fry even though they are both from the Poeciliidae fish family.

We have seen a small number of reports from people reporting that they have had a pregnant swordtail or molly when the only other fish in the tank was a swordtail or molly but the majority of the time, it seems to be due to a new fish being added to a tank and that fish already being pregnant.

This is why there are a few reports online about swordtail molly hybrid fish online but once you dig a little deeper, there is usually a simple explanation.

That said though, mollies are becoming a very popular fish to breed hybrids with and the “muppy” molly guppy hybrid is slowly increasing in popularity.

We have a dedicated article online going over everything you need to know about muppies if you are interested in hybrid fish though.

What Size Tank Does A Swordtail Molly Need?

The ideal tank size for a swordtail molly setup is usually twenty gallons or more but some people have very small setups with two or three fish in smaller fifteen gallon tanks too.

We would never recommend that you go with a tank smaller than fifteen gallons though as it can stress the fish out and result in displays of aggression.

Thankfully, there are a number of excellent 20 gallon fish tanks on the market these days that are very budget-friendly.

This makes it very easy for even a beginner to fish keeping who is on a tight budget to get a great quality fish tank that is suitable for swordtail mollies without breaking the bank.

If you are considering keeping a large number of swordtail mollies, especially if you are wanting to keep both mollies and swordtails in the same take, then trying to get a larger tank is a good idea if your budget allows for it.

Although some people will go as high as a 50 gallon tank for a large number of fish, it is usually not required and something between 30 to 40 gallons should be enough for a large number of mollies or swordtails.

What Do Swordtail Mollies Eat?

Swordtail mollies tend to do very well on a flake or pellet based food with flake based foods usually being slightly better for color retention while also being slightly cheaper in most cases.

You can also supplement the diet of a swordtail molly with various types of live or frozen food too as it can top up the nutritional profile of the diet of your fish while also adding some mental stimulation while chasing the live food.

In our opinion, the best primary food option for a swordtail molly is the Tetra tropical fish flake crips. They are cheap, easy to find, and offer an almost complete nutritional profile for swordtail mollies.

On top of this, they have various additional ingredients in the food to try and keep your fish looking as bright and colorful as possible to help reduce the chances of color fade occurring.

Although some people don’t like the idea of live feeding their fish, it can be a great way to add some mental stimulation to the diet of your fish with minimal effort being required on your part.

In our opinion, daphnia or brine shrimp are probably the best options for live feeding swordtail mollies. If you don’t like live feeding your fish then freeze dried brine shrimp can be a great alternative.

What Are Good Swordtail Molly Tank Mates?

Swordtail mollies do well with a number of different fish as tank mates with Dwarf Cichlids, Rams, Discus, Keyhole Cichlids, and Severums usually being the more popular options that people keep.

Ideally, you should be having a 20 gallon aquarium for mixing these types of fish with a 30 gallon aquarium being ideal if possible.

If you have a tank over 50 gallons then you are able to easily add a much wider range of tank mates to the aquariums due to the additional size helping to keep potential problems with aggression to a minimum.

Even though swordtail mollies tend not to be aggressive, if they are stressed or anxious due to being in a small tank or an overcrowded tank then they can display signs of aggression.

Due to there being so many different colors and patterns that you are able to find swordtail mollies in then some people will only stock a tank with them to help reduce issues and try to get the rarest colors and patterns possible.

This is why some of the rare colors and patterns costing around $50 per fish with the very rare ones being considerably higher.


That brings our article going over swordtail molly fish to an end. We hope that we have been able to help as many of our readers as possible by answering some f the more commonly asked questions that we have noticed people asking time and time again.