copper effect on green moray eel

[uscpmpdjscott]

can anyone tell me what effect copper can have on my eel?
he has not ate in about two weeks
he opens his mouth like he wants to eat but will not shut it and swallow the food???
could this be from copper i added to treat my fish?
any help would be greatly appreicated!

thanks

 

[JB_1152]

Treated a tank with copper and a very large green moray, saw no effects in him what-so-ever, still ate fine, only thing is due to a fellow feeder of the tank, he has now become spoiled to the point where I will have to hold the fillet in his mouth until he decides to swallow it. Not so much force feeding, just assisted feeding.