A photo is needed. More information from you would be helpful for us to help you.
How old is your tank? When did it originally cycle?
What kind of system do you have (tank volume, dimensions, bio-filtration method, the equipment you use, any carbon or other chemical filtration, kind of substrate, etc.).
List all specimens & sizes in the tank (fish, inverts, corals, clams, snails, crabs, shrimp, etc.).
If you have a refugium and/or sump, what is living in it?
Do you use a quarantine tank and procedure?
Foods you use and feeding schedules.
How long have you had this fish? If the fish was recently acquired (4 weeks), two more questions: Do you know what sea/ocean it came from? How did you acclimate it ââ"šÂ¬Ã¢â‚¬Å“ what procedure?
Do you use any vitamins? Fat additives? Any elemental or other additives? Please list all.
Chemistries ââ"šÂ¬Ã¢â‚¬Å“ please give actual numbers (Ammonia, Nitrite, Nitrate, Phosphate, Silica, Ca, Alk., and any others you have)
Water parameters ââ"šÂ¬Ã¢â‚¬Å“ please give actual numbers (pH and your pH range, salinity or sp. gr. & range, temperature range)
Do you see any of the following in your system: hair algae; micro algae;cyanobacteria growths; dinoflagellate (zooxanthellae) growths; brown algae; diatom growth; slimes; colored patches on rock or substrate; etc.?
Water changes (how much and how often). Kind of artificial salt youââ"šÂ¬Ã¢"žÂ¢re using.
List what you added or taken out of your aquarium system (living, decorations, and equipment) during the past 6 weeks.
Maintenance schedule. What have you done lately?
A better description of what you see along with the photo would be useful also. Like: are they lesions? do you see blood? might the dark areas by old blood? what size are those spots?
