Although pic is not clear, it resembled Acid-Fast bacterial infection when exposed to low pH for while (maybe from shipping and/or at lfs).
with an assumption that it is so, frist choice would've been Kanamyacin. If cant obtain this med then try daily smear of Bacitracin Ointment (thats right!) on the wound. Water and oil dont mix well so any excess will just fall off. JUST DAILY SMEAR and DONT APPLY TO GILL.
Hope this works whatever fish maybe suffering from. Good Luck!
BTW, Bacintracin Ointment worked well for few decades for many fin rots/lesions, etc. including the ones I catch from the beach to keep at home (puffers, butterflys, seahorses,etc..)
with an assumption that it is so, frist choice would've been Kanamyacin. If cant obtain this med then try daily smear of Bacitracin Ointment (thats right!) on the wound. Water and oil dont mix well so any excess will just fall off. JUST DAILY SMEAR and DONT APPLY TO GILL.
Hope this works whatever fish maybe suffering from. Good Luck!
BTW, Bacintracin Ointment worked well for few decades for many fin rots/lesions, etc. including the ones I catch from the beach to keep at home (puffers, butterflys, seahorses,etc..)