Platy Problems - Dealing With a Bully

Updated on August 28, 2017
A male Marigold Platy.
A male Marigold Platy. | Source

Our family home seemed empty, and like many others, we wanted a pet to liven the place up and teach the little one about caring for an animal.

After much consideration, we made the decision to purchase our first fish tank and set up an aquarium. We selected our gravel, a few smooth pebbles, a plastic reef, some plastic foliage, a little cavern for the fish to hide in, and a marimo moss ball.

We then carefully prepared our tank before purchasing our fish.

It took a couple of months to get the water levels right, mainly due to "new gravel syndrome", but once the conditions were okay, it was time to welcome some fish friends to their new home. As beginners, we didn't want to push our luck, so researched the species that would do well in our tank.

A male Mickey Mouse Platy. You can tell the sex of these fish easily, as the female has a rounded fin on her belly (known as the anal fin), whilst the male's is pointed.
A male Mickey Mouse Platy. You can tell the sex of these fish easily, as the female has a rounded fin on her belly (known as the anal fin), whilst the male's is pointed. | Source

Researching our Species

We decided to set up our 10 gallon tank as a temperate freshwater aquarium, as this would be the easiest to take care of. When dealing with live animals, we didn't want to risk providing them with a habitat that was difficult for us to manage. Being new to the hobby of aquatics, we knew it was best to start off small!

After researching our species, we decided on Platys, and one Hong Kong Pleco. Described as colourful and placid, the Platy is a member of the Poeciliidae family, and like guppies and mollies, will give birth to live young.

We read up on their behaviour, and learned that they like to be in a small group. Due to the size of our tank, we chose three females so as not to overcrowd them. We had been warned that bringing more than one male into the tank with a low female population, would cause trouble as they fight for the right to breed. The males would also harass the females.

So the day came when we purchased our girls; a light orange one, a grey one with red markings and a "mickey mouse" pattern on her tail, and a dark grey one with a grey tummy and blue in the dark scales.

All of the fish settled well into their new home, and dealt well with their water changes and tank cleans. One of them even gave birth, and our little aquarium was a joy for us all. But then the trouble began...

Aggressive Fish

Our fish soon relaxed and began to show off their own personalities. We chose names for them; Sunny for the golden one, Minnie for the grey one, and Goth for the dark one, as this fish enjoyed hiding in the dark then coming out and doing silly dances. If only we had known, this dancing was a warning sign of things to come!

Sunny was a gentle and playful fish, always eager to engage with the other two. Minnie was easy-going, but Goth soon started showing some strange behaviours.

At feeding time, she would snatch a flake and steal it off to eat it away from the others. She would then chase the other fish away to make sure that she ate first. It became apparent that Goth wanted to be the dominant fish.

Shortly after, we hardly saw her, but a few days later, fry appeared. Could it have been hormones? The Platys were in a mixed tank when we purchased them, so she would have been pregnant. That might explain the chasing; we thought she was protecting her fry.

But no. She ate them.

Then the real fun started. Her aggression became more pronounced, and she would constantly keep her dorsal fin raised to show the other girls who was boss. Chasing, nipping, and charging at them, she would push them about.

We realised how serious things had become when Sunny stopped eating. A once cheerful and carefree fish now spent her days hiding in the cavern. Her colour paled, and whilst Minnie and Goth bulked up, Sunny seemed only half their size.

What could we do?

The aggression seen in this video is due to the aquarium owner purchasing four males. They are prone to fight each other, so if you don't want mixed sexes in your tank, select females instead.

Suggested Solutions

We looked everywhere for advice. From internet forums, to the aquarium where we purchased the fish, we tried our best to resolve this.

One suggested "time out" for the bully. This method involved catching the aggressive fish and placing it in a large container for a few hours. Then, rearrange the aquarium scenery, before returning the fish to the tank.

Another suggested putting a mirror in the tank so the bully would think its reflection was another fish, and take out any aggression on the reflection.

To encourage Sunny to eat something, we also tried varying the diet more.

But nothing seemed to work, and as Sunny's health deteriorated, Goth started to take it out on Minnie.

A Sad Day

Finally, Sunny could take it no longer. The poor creature swam into the coral feature and passed away. We found her in the morning being cannibalised by the fish that had bullied her to death. It was heartbreaking.

I believe that the stress of being the victim of such aggression led to Sunny's death, and I could not look at Goth without disliking the creature. But it is just an animal doing what they do, so I had to think of a way forward to prevent this happening again.

There was only one solution. Remove the bully from the aquarium.

I did not want to euthanise a perfectly healthy fish, so had a chat with the store that I purchased her from, who took her back and gave me a voucher for a replacement fish.

Another demon fish. Note the raised dorsal fin, in a display of dominance!

So What Went Wrong?

I am still not entirely sure why Goth acted in this manner.

Platys have a reputation for being amiable fish, that get along with each other. Only when you introduce two males to a tank, would you normally see any sort of aggression.

I pored over expert advice, and I think the problem was caused by mixing varieties.

It turned out that Sunny was a Marigold Platy. These fish have a reputation for being friendly and chilled out. An older variety, they are less likely to display quirky behaviours that newer varieties might suffer from. Her nature sadly meant that she did not fight back, and withdrew from the conflict.

Minnie is a Micky Mouse Platy, named because of the little mouse-shaped mark on her tail. These varieties have been known to be aggressive at times, but it is rare. Being of a tougher nature, she did not react to the stress in the same way that Sunny did, and managed to stay out of the way and continue to feed and enjoy her aquarium.

Goth, I discovered, was a Platy/Swordtail hybrid. Probably a more recent variety, bred for its colour, she had a long "sword" coming out of her tail. Swordtails are renowned for being aggressive fish, and she had inherited this trait from one of her parents.

Mixing the varieties here, seemed to be the cause of the problem.

A male Swordtail. These more aggressive fish can breed with Platys.
A male Swordtail. These more aggressive fish can breed with Platys. | Source
Our aggressive Platy was very similar to this one, and may well be a Swordtail/Platy hybrid. Note the "sword spike" mark in her tail. Ours was even more pronounced.
Our aggressive Platy was very similar to this one, and may well be a Swordtail/Platy hybrid. Note the "sword spike" mark in her tail. Ours was even more pronounced. | Source

Moving On

As upsetting as it was, we had to carry on as we still had Minnie and our Hong Kong Pleco to care for. Sunny had a fishy funeral, and Goth was returned in disgrace to the shop where she was purchased, where she will serve her sentence in fish quarantine before being re-homed with fish of her own variety.

A water change and deep clean of the tank has been carried out, and we will be obtaining some more fish to keep Minnie and the Pleco company. However, we will be sure that we purchase the more docile varieties, such as a Marigold or Red Wag.

In Conclusion...

If you have a bully, it needs to be removed. Fish are sensitive animals and the stress will kill the victims of aggression if you ignore this behaviour.

If you do not have the luxury of a spare tank, or a very large aquarium to which you can add more fish to break up the community a bit, speak to your pet store to return the animal.

Fish are living creatures, and I would not recommend killing a perfectly healthy animal because it ruins the vibes of your chilled out tank!

If you want only one sex in the tank, choose females over males as the boys will fight.

If mixing the sexes, choose a male for every three females. More males will fight each other, and will harass and stress out the females.


    0 of 8192 characters used
    Post Comment

    No comments yet.