Koralia sucked fish in, now he's swimming weird...

[Raven34]

Sorry about that, wait awhile and replace him with something else you always wanted to get.

[Ron99]

I see you edited your post but from what I read earlier the problem is probably the type of filefish you had. They are notoriously difficult to keep in captivity and few people have had success with them. Mysis alone may not be an adequate diet to keep them healthy over the long term. They are a fish best left in the ocean or only attempted by the most experienced hobbyists.