Worried what is causing pitting lesions on my Oscar. I know for a fact my pH is high (8.2) and I have been doing sporadic water changes (sometimes waiting up to 2 weeks) over the past month. Just curious if it could be a parasite or is most likely water quality. Don't have exact readings currently but he is in a 75 gallon by himself. He started in a 55 and was moved up, overcame a short term bacterial bloom in the new tank but then the lesions (such as shown in the photo) have appeared on his head. I'd like to catch this before it affects him.