Jungle Lfie Guard. It's interesting stuff, - nothing unusual, just small amounts of things that work by themselves but are unsafe in larger concentrations: salt, acriflavine, methylene blue, nitrofurazone. Barely enough to color the water but all 4 in small amounts seem to work synergistically yet have killed the damn parasite every time I've used it. it works on a few things actually. It's similar to what pre-war aquarists used to call "pony piss" - salt, acriflavine and formalin all in small doses. It pretty much worked on everything but of course you can't sell formalin today.

They say use half strength on scaleless fish but I never bothered and didn't have a problem ever and I've only ever killed things with: salt, acriflavine, methylene blue or copper by themselves. As in every damn time. Or they wouldn't cure the disease. So yeah, I swear by this stuff. Still, what's weird is I haven't had ick in 20 years. Not putting the water from the bag for the fish store in your tank is probably a big help, dump it into a bucket through a net and put the fish in the tank, not the water from the pet store. Unless the fish is already infected this should reduce your chances of introducing the parasite by 99% (roughly)

Note also you can cure ick with a diatom filter or by putting the fish in clean water every 12 or 24 hours. Rhonda wrote an article about doing this in TFH some years back.