I honestly can't see the dfference between before and now pictures. if it's that mild, water changes will do a trick. maracyn-two is a reef and inverts safe. there are many Mardel products, so you have to make sure that it's maracyn-two and it's for salt water fish. follow the treatment as they say and mark what you do and when you do it on your calendar. however, if he eats good, just do water changes, make sure to add vitamins into his food, and monitor him. do small water changes (15-25%) every day until the spot is gone. if he stops eating or the spot doesn't go away in a few days, then go for maracyn-two.