I just got back from a 1 month trip and when I checked on one of my grow out tanks my redtail / tiger shovel nose hybrid had one cloudy eye. I instructed the person taking care of my fish while we were gone to do weekly 10 percent water changes so I don't think it was water quality. There are currently 2 pacu in the same tank which are unaffected. When I left however there was also an arowana and clown knife. They both passed away while I was gone. The catfish is about 8-10 inches. There is also a light colored patch on his head between his eyes, but it could be that he just ran into something. If you know a way to treat this or even what it is it would be helpful as I don't know if it is harmful.