When I treat for Ick, I usually just use salt (NaCl), 3lbs per 100 gallons, which produces a salinitty of 3ppt
3 ppt salinity is osmotically strong enough to kill emerging ick, but not strong enough or toxic enough to kill beneficial bacteria..
That osmotic pressure "can" be hard on some fresh water plants though.
The last time I used salt treatment, it temporarily set back my sword plants, killed java fern, but did not harm Vallisneria (in fact their is some research that shows 3ppt salinity is actually good for Vals)
By the way... the term "salt" refers to NaCl (rock salt, water softener salt, sea salt), it does not mean you need to use some jacked up priced and expensive Aquarium Salt. Salt is Salt.
Theoretically all the meds that contain ingredients like malachite green, copper, methyl red, or methaline blue do the same exact thing, they alter the osmotic consistency of the water to kill emerging ick, but......they are no more special or more effective than salt.
They are slightly more toxic though, and some are carcinogenic, if over done.