Sound pretty much right, another thing that may help would be a UV sterilizer. Keep in mind that prob 90% of tanks have ich and it is pretty easy to live with without it killing everything. A fish would have to pretty stressed as ich isn't the fastest killer. Being clowns they should be able to fight it off on there own but make sure water and husbandry are good as poor water will stress fish and reduce slime coat and cause fish to be more susceptible to ich. I believe that the only real way to rid a system of ich is by correct and strickt qt procedures but very difficult to do. Also for what it's work look up brooklynella :)