In the 4 years Ive had my tanks Ive never added chemicals to any of them.just a week ago I restarted my protien skimmer, I seen in a book today that could be a reason for his eyes I shut it off. my local lfs doesnt have great test kits I will get one the best one I can And do tests. At night time his eyes the swelling goes down but in the morning they swell back up.