I need help treating a long horned cowfish for cloudy eye. The fish is full size at least 10 inches from snout to tail. He is currently in a saltwater pond (1000 +gallons) that has been running for several years. Quarentining him is going to be tough but treating the whole pond is going to be very expensive. Has anyone had any luck with freshwater dips or medicated dips for cloudy eye? It is pretty bad, he has probably already lost his eye

I need to make sure it doesnt spread to the other fish or take his other eye... poor guy.
This fish is 5 years old but the film over his eye appeared over a few days so I dont think it is cataracts. Thank you for your help!
Edit: I did some research.... it looks like if it is caused by flukes it could get rid of it but only on him obviously... he could just get reinfested when put back into the pond...