.....
i forgot to add, which is a huge part of why he might not be chasing down his food is the fact that he has black ich......
WOW...I missed this part.....
I would seriously try and beg/steal/borrow a tank for quarantine....DO a FW dip with formalin, then treat with an anti-protozoal medicine...You wont get this outta your tank by syphoning i am afraid...as long as the fish is in the tank, the infection wont go away.....