It looks like a bacterial infection which is usually secondary infection after a possible injury or as you suspect ich. I don't see the white spots I would expect to see on the fins and rest of the body that make it pretty easy to spot. Does he seem to be rubbing up against rocks, plants glass etc.? If it were fungal I would expect it to look white and fuzzy but that's not to say it not, its hard to tell from the pic
Dan
Just to add you want to remove activated carbon or purigen from your filter when dosing medications.
Dan
Just to add you want to remove activated carbon or purigen from your filter when dosing medications.