Genicanthus Agression questions

[Tommypantsmagee]

Question for anyone who has experience with Genicanthus harems-
Do they become "Extra" aggressive and dominant during the transition from female to male?
We have 3 Genicanthus is a 6ft 220G tank, 2 Watanabei and a Melanospilos. The 2 Watanabeis were the original 2 fish, gotten as a pair of females and introduced to the tank exactly 1 year ago today, 9/262/2025. We added the new Melanospilos 1 month ago, 8/26/2026. For the first 3 weeks of them all being together they were fine, some slight aggression and chasing but seemed normal.
Then 1 week ago exactly on 9/19/2026 we came home from work to find that the largest watanabei had changed sex. Literally while we were at work he went from looking like a female to having stripes, and since then the stripes have been getting bigger and more pronounced and you can tell he is in full transition to dominant male. Well since this change has started, he has become ALOT more aggressive, specially towards the female melanospilos.
I guess what we are wondering is if its normal for there to be this big jolt of extra aggression as the hormones are changing and hes becoming more dominant and then he will kind of chill out a little bit or should we be worried that this will continue forever with him bullying her?
she has been hiding out in the top corner of the tank above a powerhead alot of the time and he will come chasing her from across the tank and she has to do these weird circles to try and get away from him. I have noticed some marks on her that look like hes nipped at her, but nothing too bad as of yet, but Im worried that he may stress her out to the point of exhaustion or death eventually.

She still eats like a pig during feedings, and is in the middle of the pack of fish, sometimes even grabbing food from in front of the other angels, so i know thats a good sign, but were just worried and looking for some advice or experiences from others who have kept mixed hereems.

What would be the point at which we should try and do something, and what would that something be?

Would putting one of them back into the acclimation box again do any good or not? The new female melanospilos WAS introduced using an acclimation box originally, but like we said, we didn't really see any TRUE aggression until he started his sex change.

Any advice is appreciated, we want the new fish to do well long term. Thanks.

 

[Damage12]

I never noticed any aggression when one of my 2 female Watanabei’s was changing to male but then again, I never mix other fish from the same genus.

 

[Tommypantsmagee]

Thanks. We can see multiple spots were she has been nipped at on her side that maybe look like a missing scale or something, and the male was just visibly nipping at her all over from her fins to her side.
We actually ended up just catching her and shes now in the acclimation box. She also has a tear in her dorsal fin but i think that came from us netting her and getting her into the box.

The male is now going around the box and trying to get in from all sides. I guess all we can do at this point is hope that he gets it out of his system and chills out

but the melanospilos can now get some time to recover away from his attacks and she is still eating in the box.

 

[Damage12]

Thanks. We can see multiple spots were she has been nipped at on her side that maybe look like a missing scale or something, and the male was just visibly nipping at her all over from her fins to her side.
We actually ended up just catching her and shes now in the acclimation box. She also has a tear in her dorsal fin but i think that came from us netting her and getting her into the box.

The male is now going around the box and trying to get in from all sides. I guess all we can do at this point is hope that he gets it out of his system and chills out

but the melanospilos can now get some time to recover away from his attacks and she is still eating in the box.

Best of luck to you.