Hi all, I’ve had a tank for a few years but I’d still say I’m a rookie in knowledge. I picked up this blue damsel today and I’ve noticed this mark once it was swimming around in my tank.
I don’t have a quarantine tank as it’s not possible at the moment, so I can’t remove it from the tank. Is this an injury from exploring the new tank or an illness that needs treating, please? I took the best picture I could.
If it does need treatment the tank is fish only so hopefully I will be able to use medicine as there are no invertebrates or corals.

I don’t have a quarantine tank as it’s not possible at the moment, so I can’t remove it from the tank. Is this an injury from exploring the new tank or an illness that needs treating, please? I took the best picture I could.
If it does need treatment the tank is fish only so hopefully I will be able to use medicine as there are no invertebrates or corals.


