When to add the aggressive fish back to the tank?

bangbang · Nov 30, 2025

I have a convict tang that went rogue yesterday after 45 days of staying together and was after all the 3 yellow tangs in my tank.. I tried feeding more, mirror trick.. but nothing would budge him.. it didn’t eat and didn’t let others eat.. consistently pestering the yellow tangs, mainly the biggest one who had moderately bad damaged dorsal fin, though the other 2 had some damage too.. after an hour of trying I could catch it and moved it to the sump..

Question:

How long shall I keep it in the sump?

When to add it back to the tank? Will it behave after whatever period or be back to being a Convict (pun intended)?

Given it was so hard to catch it, is it even worth trying to re-add it or shall I just rehome it? Anybody with similar experience?

Here is a small video of the constant chasing and damage to yellow tang’s dorsal fin (it was non stop chasing and trying to nip at the fins)

Largeangels · Nov 30, 2025

I’d sell it or trade it to the LFS. Convict tang was the nastiest tang I’ve had and I have sohol, clown, powder blue and purple. Was fine for a few years then went after the powder blue non stop! Nothing worked. So back it went.

Marco_99 · Nov 30, 2025

Video didn’t post. A little more backstory might help. How long has what tangs been in the tank, tank size, how old are the tangs. Time outs alone usually don’t remedy if the convict is just being territorial. You’ll have to time out and change up his claimed territory if that’s the issue. A week or 2 minimum

larrysaltisfun · Nov 30, 2025

bangbang said:
I have a convict tang that went rogue yesterday after 45 days of staying together and was after all the 3 yellow tangs in my tank.. I tried feeding more, mirror trick.. but nothing would budge him.. it didn’t eat and didn’t let others eat.. consistently pestering the yellow tangs, mainly the biggest one who had moderately bad damaged dorsal fin, though the other 2 had some damage too.. after an hour of trying I could catch it and moved it to the sump..

Question:

How long shall I keep it in the sump?

When to add it back to the tank? Will it behave after whatever period or be back to being a Convict (pun intended)?

Given it was so hard to catch it, is it even worth trying to re-add it or shall I just rehome it? Anybody with similar experience?

Here is a small video of the constant chasing and damage to yellow tang’s dorsal fin (it was non stop chasing and trying to nip at the fins)

That looked like pretty aggressive behavior. I would worry about what would happen at night when you put him back in and you’re not able to watch the tank. I would be worried that all three tangs could perish pretty quickly. I would not want to sacrifice three good children (let alone the fact they have become more difficult to obtain.). because of the behavior of a fourth one..
How much you gonna worry about that fish if you put him in and he’s gonna be on his good behavior initially? How much work is it gonna be to get him back out and will you get it back out in time? I don’t think anyone can give you answers to those questions. Good luck I know what you’re going through.

bangbang · Nov 30, 2025

Marco_99 said:
Video didn’t post. A little more backstory might help. How long has what tangs been in the tank, tank size, how old are the tangs. Time outs alone usually don’t remedy if the convict is just being territorial. You’ll have to time out and change up his claimed territory if that’s the issue. A week or 2 minimum

It’s a YT link.. The tank was recently setup, all fish were added to the tank at the same time about 45-50 days ago.. they all have lived in harmony except the 1st week when defining territory.. I lost a PBT to ich after which I went hypo a week ago.. I also turned off the lights since I had a pretty bad cyano issue and since it’s a FOWLR tank, I just didn’t want to turn them on anymore.. these 2 may be stressful events for the fish, since with no light, they have less algae to graze on meaning more competition.. also hypo in itself maybe causing some stress.. I loved this healthy convict tang, it would be a bummer to let it go :( But once a bad guy, always a bad guy theory may prove to be true on this case.. anybody has experience with re-adding the fish from the sump back to the tank? Did the bullying subside? How much time in sump did it take? Its painful to take them out of the tank, otherwise I would have definitely given him a 2nd chance

vetteguy53081 · Nov 30, 2025

bangbang said:
I have a convict tang that went rogue yesterday after 45 days of staying together and was after all the 3 yellow tangs in my tank.. I tried feeding more, mirror trick.. but nothing would budge him.. it didn’t eat and didn’t let others eat.. consistently pestering the yellow tangs, mainly the biggest one who had moderately bad damaged dorsal fin, though the other 2 had some damage too.. after an hour of trying I could catch it and moved it to the sump..

Question:

How long shall I keep it in the sump?

When to add it back to the tank? Will it behave after whatever period or be back to being a Convict (pun intended)?

Given it was so hard to catch it, is it even worth trying to re-add it or shall I just rehome it? Anybody with similar experience?

Here is a small video of the constant chasing and damage to yellow tang’s dorsal fin (it was non stop chasing and trying to nip at the fins)

I have a purple in the sump for over 2 months. Im waiting until 90 days