Swordtail not doing so great

20g with three male swordtails and two male platy. Platy are fine. Biggest swordtail definitely seems to bully one of the other swordtails. He mostly keeps to a corner behind some decorations but does eat fine. Pic shows his top fin pulled in which I think is a sign of stress, no?

What do you do with a bully like this?

Water quality is fine, testing multiple times a day. Today was my last day of treating the tank for ich. This particular swordtail had a lot of spots but they are all gone and overall for the most part all five fish seemingly have dealt with the med (nox ich) and temp increase to 81 fine.

Just for comparison, here's the same fish last week before ich treatment

Hi, can you get a photo of the whole tank so I can see the layout please?

Sure here you go

Hmmm, it's quite open.
Male livebearers can pick on each other sometimes, especially when there are no females around to distract them! Not that you should add females unless you want/are prepared for breeding, since livebearers produce so many fry, and a male only tank can work, it just takes a bit more planning and thought, and monitoring for bullies.

Firstly, fill the tank with more plants, driftwood, things that break lines of sight and providing hiding spots. You have a lot of that lower down, but the top is very open and exposed, and the bully can spot the smaller male easily, so he's more likely to relentlessly chase, you know? I'd add some floating plants with long roots like frogbit or water lettuce, these provide some dense cover, and fish tend to feel safer with overhead vegetation too.

I'd add some big bunches of live plants, some hornwort, elodea or water wisteria, some fast growing stem plants like that that can be left floating in a dense plant mass near the surface, or planted and allowed to grow tall, and that would provide cover throughout the whole height of the tank, you know? Or vallisenaria... grows tall and can be cultured into some pretty dense curtains of plant, great for hiding spots the whole tank height. Taller pieces of driftwood or stone can provide some additional structures with height to help. Live plants provide some environmental enrichment for the fish, since they interact with live plants in a way that they just don't with fake ones, and they help with water quality too, win win!

Will use my own tank to demonstate what I mean, so I don't have to steal some random photos fromgoogle. This tank is less than a month old:


So it hasn't fully grown in yet, but see the top right? The wood, some vallis, and the frogbit already form lot of hiding space there, and breaks line of sight between fish, so the bullied one can get away and get some peace, and the bully is more likely to lose sight of him and forget about him for a while, or get distracting eating algae from another plant. Doesn't necessarily have to be real plants either, the main point is to have structures of some kind that will break up the tank into areas, and give the fish places to hide and explore, alleviating boredom and reducing the harassment.


A couple of young platy fry, hiding out in the frogbit roots



If doing some tank renovations doesn't help, then adding a couple more males might. Since there are only the five fish in a 20 gallon, you have room for a few more, and it could disperse the aggression and keep the bully busy, so he isn't so focused on pestering the one fish.

If that also fails, try removing the bully male to a temporary holding tank (a bucket with an airstone and kept to the same temp and covered with a towel to prevent jumping can work) rearrange everything in the tank, and leave the others in there for a while, let them explore and establish new territories. Add the bully male back in. The idea is that it will look like a new area to him, like he's moved to a new area in the river, and it's not his old familiar territory anymore. He's more likely to find himself feeling like the new guy, will have to establish a new spot in the tank as his new territory and they others already have theirs, so he has to find his own, and it's not the whole tank anymore.

This sometimes works - African cichlid keepers use this method a lot! But, it doesn't always work either.

If all of those fail, then one or the other will need to be moved out permanently.

also keep an eye on how the others interact with the weaker male. If all of the fish are picking on one fish, that is often a sign that there's something wrong with the one that's being bullied. Fish torment a sickly fish. Sounds mean, but sick, struggling or dying fish attract predators. It's in a fishes nature to drive away another fish that is sick, since it could draw a predator right to them. It's another good reason to move a sick or dying fish to a quarantine tank, not only to reduce the chances of spreading the illness.

Thank you, wow what a great reply. So many insights. I don't think I have the time or energy to do a live planted tank but I will look for something higher to put in there. When it isn't feeding time, the bullied mostly hangs in the corner behind the root decoration. It's weird because I actually saw the bully in the corner with him today and they were just chilling out together.

He goes after the Platies, especially during feeding time, but they seem resilient to it all and totally unphased - he turns around and they are back in his space.

I'm going to do a water change tomorrow so maybe I'll rearrange or add something new. Eventually, I'd like to add a few more fish either some glofish or a few bottom feeders.

The bullied fish seem to be the worse off with ich last week but it's all cleared up now. Probably wasn't helping him stand up for himself.

You're welcome, I hope it helps. Remember to move the bully fish out while you re-arrange the tank.

I'd add another couple of male swords, so he sees them as competition and is less likely to focus on that one other male swordtail. Then by all means, add some glofish

No time or energy required if you just add some floating plants like the frogbit or water lettuce, or red root floaters, I promise! They manage themselves, no trimming or planting needed, you just need to remove and bin the odd handful when they take over too much of the surface, which takes 30 seconds when you're doing maintenance Certainly easier than going full planted tank! I bought a small pot of the frogbit for around five bucks, and I'll never need to buy more, it's grown and spread that much in three weeks, and has those lovely long roots for hiding in.

Or, I think it was @Deanasue who shared a fake floating plant, was it fake anacharis or something that floated on the surface? Only available in the US? Hoping you can share it here for OP! Or any other tips since you've had/have livebearers too!

Bottom feeder wise, you might be able to do a bristlenose pleco, but bear in mind that fish like corydoras and loaches need a sand substrate, they're not suited to gravel since cories filter feed and can't do that on gravel, and khuli and dojo loaches have soft bodies and will bury themselves in sand, but can't do that in gravel. Plecos are okay on gravel though.

Let us know how it goes!
Also keep in mind that now and then, there will be a male who is just a relentless bully, no matter what you do.
I've kept male only guppy tanks when I was growing out males before they went to the store, had 30 odd young male guppies in a tank at one point, and all were great, except for one, who was a devil. He was mean and pesistent, and dense planting or any other measures did nothing to stop him. Remove his favourite target, and he'd just pick another one to target. 30 odd peaceful males, but one who was just.. a nightmare. lol. He wouldn't have been happy except in a tank with a dozen females all to himself, he was just too driven to live in a male only tank, so I was relieved when he went to the store.

So if all else fails, you might have a male like Diablo on your hands.

I don’t keep Livebearers. Mine are egg layers but here’s the plant.

AdoraBelle Dearheart said:

You're welcome, I hope it helps. Remember to move the bully fish out while you re-arrange the tank.

I'd add another couple of male swords, so he sees them as competition and is less likely to focus on that one other male swordtail. Then by all means, add some glofish

No time or energy required if you just add some floating plants like the frogbit or water lettuce, or red root floaters, I promise! They manage themselves, no trimming or planting needed, you just need to remove and bin the odd handful when they take over too much of the surface, which takes 30 seconds when you're doing maintenance Certainly easier than going full planted tank! I bought a small pot of the frogbit for around five bucks, and I'll never need to buy more, it's grown and spread that much in three weeks, and has those lovely long roots for hiding in.

Or, I think it was @Deanasue who shared a fake floating plant, was it fake anacharis or something that floated on the surface? Only available in the US? Hoping you can share it here for OP! Or any other tips since you've had/have livebearers too!

Bottom feeder wise, you might be able to do a bristlenose pleco, but bear in mind that fish like corydoras and loaches need a sand substrate, they're not suited to gravel since cories filter feed and can't do that on gravel, and khuli and dojo loaches have soft bodies and will bury themselves in sand, but can't do that in gravel. Plecos are okay on gravel though.

Let us know how it goes!
Also keep in mind that now and then, there will be a male who is just a relentless bully, no matter what you do.
I've kept male only guppy tanks when I was growing out males before they went to the store, had 30 odd young male guppies in a tank at one point, and all were great, except for one, who was a devil. He was mean and pesistent, and dense planting or any other measures did nothing to stop him. Remove his favourite target, and he'd just pick another one to target. 30 odd peaceful males, but one who was just.. a nightmare. lol. He wouldn't have been happy except in a tank with a dozen females all to himself, he was just too driven to live in a male only tank, so I was relieved when he went to the store.

So if all else fails, you might have a male like Diablo on your hands.

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Deanasue said:

I don’t keep Livebearers. Mine are egg layers but here’s the plant.

Click to expand...

Think you forgot the link

Oh sorry, I just watched your video from when you won tank of the month earlier today when I was looking at past winners, and saw you had male guppies in there, but that was a while ago

“Or, I think it was @Deanasue who shared a fake floating plant, was it fake anacharis or something that floated on the surface? Only available in the US? Hoping you can share it here for OP! Or any other tips since you've had/have livebearers too!”

I actually don’t keep Livebearers. Got rid of them couple of years ago. I only have egg layers. Here’s the plant. Though.

AdoraBelle Dearheart said:

Think you forgot the link

Oh sorry, I just watched your video from when you won tank of the month earlier today when I was looking at past winners, and saw you had male guppies in there, but that was a while ago

Click to expand...

Yeah, I got tired of babies from the platies. I would have kept the guppies but they didn’t do well with my water.

The fish in the original post has clamped fins, a damaged tail and is covered in excess mucous.

Clamped fins can be caused by poor water quality, external protozoans, fungus or bacteria.

Excess mucous is caused by something in the water stressing the fish. It can be caused by poor water quality, chemicals/ medications or external protozoan infections.

If you used an anti-parasite medication it should kill off any external protozoan parasites. However, you might have slightly overdosed the fish and that is stressing it out.

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Bullying will not cause excess mucous but does stress the fish and weaken it, allowing diseases and parasites to infect it.

If one fish is bullying the other, you need to separate them, put them in different tanks or get rid of one.

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Right now I would wait a day or two and then do a big (75-80%) water change and gravel clean the substrate. This will dilute any medication in the water.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

You can clean the filter too if it hasn't been done in the last 2 weeks. Wash filter media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the lawn.

Then see how the fish looks after the water change. If it doesn't improve within 24 hour of the water change, post more pictures.

So my bulky swordtail doesn't have anyone to bully anymore. The two other sickly swordtails died yesterday. He seems to get along just fine with the two remaining platy, all three seem healthy at this point. I'm going to focus on getting the ammonia down and tank cycled. Water changes, prime, testing.