I've not used it, but I have gotten rid of ich a few times from different fish using a diatom filter.
It says it can pull out anything bigger than 1 micron (including the swimming - infectious - stage of ich). I was skeptical, but it has worked very well. No chemicals and I've had a 100% success rate and zero lost fish with it.
As an added benefit, it really cleans up the water. I use it on my quarantine tank about once a week to keep it good and clean (using a turkey baster to stir everything up & it sucks it out)