I would not use the filter. And i would be consistant with water changes also. Just try to do for now 50% and 1-100% a week. I am going to pm you my e mail so you can send me a picture. If he is eating and swimming , and there is no behavior changes at all i would just do regular water changes , unless his fins are really bad-bloody tips, falling apart,large part of the tail just drop off,ragged edges,black edging that are ''smudged'' all those symptoms are for the fin rot. I don't remember if you have stress coat, it good for healing. Now about'' fix'' medications do not use it . I am going to pm you my e mail and also will give you the link about melafix or any medicine with ''fix''.