Guppies Chasing Platy And Molly Fish: Reasons & Solutions

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Growing fish in community tanks could be challenging, especially when you encounter aggressive behavior from one tankmate to another. For instance, I noticed that my guppy is chasing either my platy or molly fish quite frequently. To solve that problem, I started researching all the potential causes for the annoying issue.

Guppies typically chase platy and molly fish for mating purposes. Male guppies frequently attempt to breed with mollies and platies when the tank lacks female guppies. However, that also happens under stressful conditions, like low water quality, overcrowded tanks, and territorial struggles.

As we move forward in this article, I will share a few tips to help you raise guppies, platies, and mollies peacefully in the same tank. Hopefully, that will keep your guppies from chasing their tankmates.

Why Is My Guppy Chasing My Platy & Molly?

It isn’t necessarily normal for guppies to chase other fish, such as platies and mollies. But it happens. However, because guppies have peaceful temperaments, only a small number of reasons would compel them to act aggressively towards a molly and platy, including:

1. Mating Purposes

Guppies are very enthusiastic breeders, and you rarely have to push them to reproduce. In fact, they have a reputation for harassing their female counterparts.[1] If your tank doesn’t have enough female guppies, the male fish will direct their frustration towards the female mollies and platies in the aquarium.

These three species are quite similar to one another in shape and average size. The small differences that separate them are unlikely to prevent a guppy from attacking a female molly or platy for mating purposes.

2. Competition

Male guppies don’t stop at harassing female guppies. They will also fight other male guppies to attract the attention of the females. If the platies and mollies in your tank are male, they could become the targets of a competitive male guppy determined to mate with the few females in the tank.

Such aggression is rare in aquariums that have female fish in sufficient numbers. However, even if you have no idea what genders you’ve picked at the store, this issue rarely occurs. Statistically, most aquariums have about the same number of male and female fish, even if picked randomly.

3. Territorial Struggles

Guppies have territorial tendencies. This attribute isn’t prominent in the species, but it exists. If the tank is crowded, your guppies might lash out against their neighbors as a way of securing space for their kind.

You may suspect that this is your case if your guppies are chasing your molly or platy once they have approached their environment. If you observe carefully, you will notice that certain fish in the aquarium spend most of their time in the same place. That would be their territory.

4. Poor Water Quality

Dirty water, the kind that has high concentrations of toxins like ammonia, is harmful to guppies. It will induce stress, which can compel the fish to react unpredictably and aggressively. You might encounter similar behavior among sick guppies.

Some people believe that starvation can attract hostility from guppies. But if your guppies are not eating enough, the same is probably true for the mollies and platies. In that case, they will all resort to aggression and violence. Guppies are not the only fish that respond negatively to discomfort.

Can Guppies Live With Platies And Mollies?

Guppies can live with platies and mollies.[2] All three are live-bearing fish that share several attributes, so they are suitable tankmates for one another. Therefore, if your guppy is chasing your platy or molly fish, there is very likely an underlying cause.

These factors support the fact that guppies, platies, and mollies can live peacefully in the same tank: 

1. Minor Size Differences

All three fish are similar in size, which means they are unlikely to perceive one another as food. Large fish with peaceful temperaments typically eat smaller fish simply because the creatures can fit in their mouths. 

That is why aquarists are cautioned against pairing fish whose sizes vary so drastically. But that isn’t an issue here. It is unlikely that the guppy fish feels superiority over the platy or molly due to size differences, significantly when all three have fully matured.

2. Temperament

All three species are categorized as peaceful and social. Mollies are considered the most social of the bunch.[3] However, all three species prefer to live in groups. Platies are not necessarily shoaling fish, but they are happiest in small communities.[4]

The three fish’s docile temperament also allows them to live in mixed groups and not necessarily stick to their kind. In other words, it is possible to grow a group of molly, platy, and guppy fish as one unit without experiencing any issues.

3. Similar Tank Requirements

All three species thrive in similar tank conditions. They need roughly 20 gallons, pH levels ranging between 6.0 and 8.0, and a temperature of 64 to 82 degrees F. They also have the same maintenance requirements, including the frequency of the water changes.[5]

They even eat the same food since all three fish are omnivorous. That means that they consume both animal and plant matter. Therefore, it isn’t an issue to keep all three satiated. You can use regular fish food, which typically consists of pellets and flakes.

Also Read: Can Molly Fish And Guppies Live Together?

How To Make Guppies, Platies And Mollies Coexist?

Even though guppies, platies, and mollies have peaceful temperaments, conflicts can still break out. That is why you might have seen your guppy chasing your molly or platy. To maintain a tranquil tank, you must identify and resolve the sources of these conflicts:

1. Choose The Right Tank Size

You wouldn’t expect the tank size to present much of a challenge. After all, guppies, platies, and mollies are relatively small. And if you prepared adequately before buying the fish, you probably took the time to secure a generously sized aquarium.

But things are not quite as simple as you might presume. Platies are your biggest concern on that matter. They breed at such a rapid pace that they could eventually overwhelm your tank with fry. And once those fry mature into adult fish, they will crowd the tank.

You have to take the breeding habits of all three fish into account when purchasing a tank. Even though they can survive in a 10-gallon unit, you are better off buying a tank of 30 gallons or more to accommodate unexpected fry explosions.

2. Pick The Right Male-To-Female Ratio

Because these fish are so relentless where breeding is concerned, your tank requires an abundance of female guppies, mollies, and platies. It would be best if you kept two to three females for every male guppy. The same is true for male platies and mollies.[6] 

A scarcity of female fish will encourage the male fish from all three species to fight one another. Guppies are particularly aggressive in this area, so it is common to see them chasing other females and males, even from different species.

3. Maintain High Water Quality

As was noted above, dirty water will antagonize your fish, causing them to react unpredictably. This matters where guppies, platies, and mollies are concerned because mollies are pretty messy creatures.[7]

All they do is eat and poop, and they are more than capable of overwhelming your tank with toxins like ammonia, especially if you have no prior experience with fish. Accumulation of ammonia may burn your fish’s gills, causing them to act aggressively.

That is why you should get a decent filter that can contend with all the waste produced by your platies. The filtration system I recommend is the MarineLand Penguin Bio-Wheel Power Filter (link to Amazon). It gets the job done in my tank while keeping out the noise.

It would be best if you also carried out regular water changes to prevent toxins from accumulating. You can know if your tank features poor water conditions using the API Aquarium Test Kit (link to Amazon). It will measure the pH, ammonia, nitrates, and nitrites within minutes.

4. Feed Your Fish Adequately

Guppies, platies, and mollies typically feed at the surface of the water.[8] And because they are social creatures, they will eat at the same time without interrupting one another. You will probably see them rush to the surface during feeding times whenever they see you.

That can present a challenge when you forget to feed them or if the meals you provide are too small. They will eventually fight one another for the available food. That is why you are encouraged to install an automatic feeder to ensure that their meals are always delivered on time, such as the Eheim Automatic Feeding Unit (link to Amazon).

You should also pour a sufficient amount of food so that your guppies aren’t getting starved. That could induce stress and encourage them to chase other fish, such as the docile mollies or platies. Feed your fish the amount they consume within two to three minutes and no less.

5. Introduce Plants & Decorations

Your tank should have plenty of hiding places.[9] If it doesn’t, I recommend adding plants, rocks, caves, or anything the fish can use to stay out of sight. Guppies, platies, and mollies feel more secure when they know that they have sanctuaries that will keep them protected from the tank’s aggressors.

However, make sure that you don’t overcrowd your tank. You should maintain that delicate balance so that your fish won’t encounter one another too frequently. That might induce aggression and encourage your guppies to chase other fish.

6. Take Care Of The Fry

None of these fish are great parents. But a guppy, platy, or molly might attack another fish that shows signs of hostility towards its young. You are more likely to see such behavior in pregnant guppies, mollies, and platies, especially when they confront fish trespassed upon their territory.

One way of resolving this issue is to place pregnant fish in breeding tanks and keep fry out of community tanks until they grow to the appropriate size. If one of your pregnant fish has already spawned, it would be easier to move the adult guppies to a different tank.

7. Reset Preexisting Territories

Your guppy may be going after you platy or molly fish as means of territory establishment. You typically see this when other fish are swimming towards areas that the guppies frequent, and the guppy reacts aggressively.

To solve that, I suggest making rearrangements to the tank. Put your plants, decorations, and rocks differently from how they were. That will reset the territories of each fish and force it to find new ones. Do that every two weeks or once you notice the aggressive behavior.

Also Read: Can Guppies And Mollies Crossbreed?


If your tank features too many male fish, your guppy will likely chase your molly or platy for mating purposes. It will try to breed with the female platies or mollies even though they are from different species. Crossbreeding is possible in some cases.

However, guppies may also chase their tankmates when the ammonia, nitrites, nitrates, or pH are out of the desired range. That is why a testing kit and frequent water changes are mandatory. You should also measure the temperature and ensure that your aquarium is large enough to accommodate the number of fish.