Need help：Pygocentrus nattereri‘s gills roll up

[trevor033911]

Have you tested your water?

Yes

If yes, what is your ammonia?

0

If yes, what is your nitrite?

0

If yes, what is your nitrate?

haven's rerw

If I did not test my water...

1. ...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.

Do you do water changes?

No

What percentage of water do you change?

0-10%

How frequently do you change your water?

Every two weeks

If I do not change my water...

1. ...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.

Hey everyone. There are around 20 Pygocentrus nattereri in my tank. And I feed them from they are very small. Recently I found they may have some gills problem. Firstly just 1 fish. Now they are around 4 fishes got this problem. The water quality is pertty good. No ammonia no nitrite. I just don't know why they got this diease. I really love these fish and feed them boiled shrimp, codfish, squid etc. But I changed the water not usually so the nitrate may a little bit high. So how to treat them. The fishbowl is 43 gallon with 6 gallon bottom filter. Thanks everyone

 

[FJB]

I don’t have experience keeping piranhas. But the tank is too small for the fish biomass, and no (or little) water changes is not likely to result in long term health, even in a large tank. Those are the issues I would address, starting with regular and large water changes. Good luck.

 

[Deadeye]

I agree with the above. I couldn’t pinpoint the exact issue, but starting with cleaner water (and a bigger tank long term) will help.
The other potential cause is piranha aggression, but I wouldn’t expect them to tear off gill plates like that.

 

[FINWIN]

Yah, looks like gill curl. I had one fish get it. I just increased water changes with a little salt and it resolved itself.

 

[trevor033911]

I don’t have experience keeping piranhas. But the tank is too small for the fish biomass, and no (or little) water changes is not likely to result in long term health, even in a large tank. Those are the issues I would address, starting with regular and large water changes. Good luck.

Thanks FJB! I'll change the water frequently. I test the nitrate is around 25-50mg/L.

 

[trevor033911]

Thanks Deadeye! I'll change the water frequently. By the way do you think this tank is a little bit small for these piranhas? My tank size is 895mm*395mm*570mm around 43 gallon with 6 gallon bottom filter.

I agree with the above. I couldn’t pinpoint the exact issue, but starting with cleaner water (and a bigger tank long term) will help.
The other potential cause is piranha aggression, but I wouldn’t expect them to tear off gill plates like that.

 

[trevor033911]

Yah, looks like gill curl. I had one fish get it. I just increased water changes with a little salt and it resolved itself.

Thanks FINWIN! This is a very useful advice. I'll try it!

 

[Deadeye]

An adult red will reach 300 mm. Even a single one would struggle to move in a tank barely wider than in. That doesn’t even begin to cover how much waste one will produce. Now multiply that by 20.
I wouldn’t think about keeping even a single piranha in less than a 6 foot long tank. The shoal size really determines how large you need to go (for 20 to not kill each other you’d need a couple hundred gallons bare minimum).