Is it just the one eye that is cloudy? It could be an injury or there could be some infection going on. I notice the fins also look a little tattered, is he being bullied by anyone? How long have you had the fish and when did you first notice the eye? Is he in QT already? You can treat with erythromycin to help clear the eye up. Also epsom salt helps to reduce swelling, 1 tablespoon per 5 gallons. It would also be a good idea to do a freshwater dip just to rule out the possibility of flukes https://www.reef2reef.com/threads/video-how-to-do-a-freshwater-dip.286639/