Captive bred Purple tang - gill extending outside

[Leon.NYC]

Hi all, I’ve had this juvenile captive bred purple tang since May 2023. He’s developed Growth on his gills which makes it protrude outwards. This started a few weeks after adding him to my main display. He eats a lot and swims In a “bouncy” motion.
Tank mates include; 2 clown fish, copperband, regal angel (juvenile), anthias. All fish were quarantined (copper, formalin/h202 & prazipro). Not necessarily sure if it could be a side effect of subjecting a juvenile to copper/formalin at that stage. Thoughts?

 

[Jay Hemdal]

Can you post a video of it swimming?

The pictures are not super clear, but the growth seems to be on the outside of the gill, not coming from underneath, right?

This isn't a result of your treatments in any way - if there was an issue with any chemical bath, it would not affect just one point of a fish like that.

It could be Lymphocystis (a mild viral disease) but it doesn't look quite like it in the photo. Given the length of time it has had this, and that it is only on one gill, you can rule out parasites.

Jay