Any ideas of why a fish would suddenly (over a period of two days) go from normalcy to completely blind? I"ve got a Royal Gramma that was at the end of his QT that seems to be completely sightless now. It's eyes look okay. Been alone in QT so no aggression by tank mates. Can't figure this one out. Oh, and final question: Does anyone have any first or secondhand knowledge of a fish ever regaining its eyesight once it's been lost? TIA