Jay what is this

[The Ugly Phase]

not my fish came across it but never seen something like that before (not the fish the disease on its side)

@Jay Hemdal

 

[vetteguy53081]

not my fish came across it but never seen something like that before (not the fish the disease on its side)

@Jay Hemdal

Looks to be a Vlamingi Tang with a bacterial issue however the image provided has a lot of reflection from the glass as well as a picture angle in which fish is not visible in whole

 

[Jay Hemdal]

not my fish came across it but never seen something like that before (not the fish the disease on its side)

@Jay Hemdal

It does look like a bacterial disease mixed in with some mucus. Given that it is on both sides, and the skin looks damaged around it, I would say that the fish had gone through some trauma - flipping around in a net or jumping out onto the floor for example.