I just finished a 2 plus week dosing of kick-ich on my 650 gallon reef tank. I've got LPS, SPS, Magnificent Anemone, Shrimp, Clams, Snails, Fish, etc. My powder blue and my hippo tang came down with it, and I dosed Kick-Ich every other day for 2+ weeks. The ich is mostly gone, but did keep coming back during the period.
None of the other items in the tank were effected by Kick-ich.
The ich took my royal gramma and a little green banded goby, but not the hippo or the powder blue tang. They slowly got better (i.e. fewer and fewer spots over the 2-3 weeks). My guesstimate on why is because of the following:
1) Kick-ich probably irritates ich, but doesn't really keep it from its reproductive cycle. I'd think of it as an ich pest, reducing its effectiveness.
2) My 6-line wrasse loves to pick the ich parasites off the tangs, and I think that the combination of the removal of the parasites with the kick-ich helped keep the fish from succumbing.
I guess I'd recommend a 6-line in your tank first and foremost, and then see if any ich picks up. Kick-ich, in my opinion, likely only helps if the fish is healthy enough to fight off the infection.
Hope this helps.