Too me there isn't any reall reefsafe medicine... unless you get a tiny tank to medicate them separately.
I just feed the fish constantly with Garlic ( helps with fish appetite and some say once in the fish's system.. .the ich dosnt like the taste of the fish after ???? ), Selcon as ( a bonding agent for food and vitamins ), Vita-C for ( Vitamin supplementation ) and you can add other stuff, I add cyclopeeze to it too ( for taste and omega fatty acids )...
doing so helps the fish stay strong to fight the ich off when it comes back during the 6 week period