Strange problem with just one fish


I am puzzled with a problem that I have, I hope someone may share some advice.

I have had this 30 gallon tank for about 5 years now:
* 3 rainbowfish
* 2 yoyo loaches and 1 zebra loach
* 4 corys
* 1 banjo catfish
* 5 gold barbs
* 1 red-tailed black shark
* 1 tiger barb

Water is 26°, 0 ammonia, 0 nitrites, around 20 nitrates, close to neutral PH, did not measure hardness for a long time.

The selection of fish is I would say "just so happened".

Everyone seems to get along well. I mean, one rainbowfish would occasionally chase another one, or red-tailed shark would have a conversation with a yoyo, but I do not sense any aggression and tension in the tank, in general. Even the tiger barb that is alone doesn't seem to care at all.

That was until I got one gold barb.

A couple of days after the first gold barb was added to the tank about a year or two ago, his side got bloody and I saw nearly everyone nipping at him as if he was dying. Surprised, I moved him to another tank where I just had one gold fish - to recover.

The barb recovered well, and after some time, I decided to reintroduce him back to the community tank. Two or three days later, again blood on the sides and fish nipping at him.

I moved him back to my single gold fish, and he spent there the next year or two.

Recently I bought 4 new gold barbs and added them to the community tank. They integrated without a problem. So then I thought - okay, maybe now that I have a kind of a colony of gold barbs there, I could move my "sufferer" back to the community tank and hopefully he stays with the school (even though he's 2.5 times bigger than the other four) and nobody touches him.

So I make the third attempt to move my old gold barb to the community tank.
First half a day he finds his place in the pecking order in the school and becomes the part of the school.

Couple of days later - AGAIN looks like blood and damage on his side near his fin.

I don't know what to think now, because the remaining four barbs are okay, it's again just the problem with this one.

Maybe someone could share some helpful tips as to why this could happen.

Thank you!


He may be really challenging the pecking order and being "put" in his place. If so seems like he hasn't learned anything after all these years.


I don't know a whole lot about barbs (sorry) but I think that blazebo is right. I had a fish that did that a lot. He stopped after a while. Maybe that'll be the case for your fish. I hope it works out


Maybe its not the barbs doing the damage, it maybe the shark

Fish Fan

I know you said your parameters are good but are they streaks like ammonia poisoning....could he allergic or more sensitive than the other fish to your water parameters...are the parameters in both tanks the same?


For some reasons I only got one notification about one response to this thread; so I was under assumption that nobody else responded and saw the other responses only now.

Regarding the parameters - in fact I think his original tank (where he cohabited with one gold fish) probably had worse parameters. I don't measure that one too often but the gold fish apparently creates a lot of mess, while this community tank whenever I measure it shows full zeroes, even if I'm sometimes late with water change.

So, to follow up on this story.

I decided to just keep watching and see what happens.

The "sufferer" gold barb, as I wrote in the first message, looked pretty bad right after the move - one of his sides and dorsal fin looked pretty bad. I decided to give it a week to see how that progresses, because despite the damage the gold barb was now swimming with the group of the other 4 gold barbs and I was hoping that he had more fun in the school than being alone with the gold fish.

He looked pretty bad for a week or so, and then started recovering; it's been a month now and he looks totally alright. The only thing that changed compared to his time in the gold fish tank is that he got more color in his dorsal fin, which I don't know how to interpret but maybe it's like with the rainbowfish - the more fun they have the more colorful they get. Just my guess though.

So I still have no explanation - either to what happened all these times, who was tearing him apart and why - or to why this time, he was able to survive this, to recover and now feels well.

My only guess is that because he stays with the school there was less aggression this time (all the previous times he was getting so bad that I had to move him to prevent him from being eaten alive), or maybe he was more confident fighting back to that unknown aggressor feeling that he's a part of a larger group now... Remains mystery to me.

But I'm glad that things (seemingly) worked out themselves, although I would really love to know what in fact happened and who always started that...

Thank you everyone for your advice!


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