ICH...maybe...You can use some type of ick/ich away medicine or put some garlic extract in it's food, let it soak and dry... feed it to the fish... i wouldn't advise u use ick medicine if you have some type of invert...(crabs,snails,shrimps,etc.) but since u said u have a fish only then.... i don't really know but get someone else's opinion... only had one out break and i used and ick medicine and put the infected fish in a quarantine tank, and afterwards added a scarlett cleaner shrimp to my main tank... no probs since...