Furan 2 works (use gloves, it's a human carcinogen!), or another antibiotic I've used in the past (cephalexin, can get from just about any vet's offfice) is another good option. A lot less toxic to mammals, and in my experience gentler on the treated zoas - I've lost noticeably fewer affected polyps when using the cephalexin approach.
Admittedly, Furan 2 works quicker in most cases - 3 days of treatment followed by a couple days "recovery time" & repeat as needed, but it's more a cure-or-kill option. The cephalexin's more a treat-daily-until-cured regimen (up to a week in past courses). In either case try one regimen, and then switch to the other if the pox return or simply don't respond.
I've also had better results using tank water for the treatment dip, not freshly mixed as zoaid.com directs. Guaranteed parameter match that way and makes the dipping process quick, thus ensuring it actually happens.

Stir the bath frequently and use a pipette/baster to gently blow dip water at the polyps.
Incidentally, how many frags/colonies are you looking at treating? You'll need to dip ALL of them to be sure of knocking it out.