I also have a black moor with popeye on one eye. I've treated him with Melafix, anti-parasite meds and salt and he has shown no recovery. How large is your moor because a 2.5 gallon is pretty small for a fish unless I guess it is still a baby. You should probably think about upgrading, toxic chemicals like ammonia can build up quickly in such small tanks without you noticing. I would suggest a 10 gallon for a moor, he would be more comfortable.