the best thing to do if you have ich in your tanks is to take out all of your fish for 6-8 weeks, basically the life cycle of the ich, if they cant find anything to cling to in order to reproduce, they will slowly die out, and this takes, on average, 6-8 weeks, and while this is going on, you can, if you have a QT tank set up, quarantine all of your fish for the 6-8 weeks at hyposalinity, which means you need to slowly, over a period of 3-7 days, take your salinity from 1.025 down to 1.009, and keep it there for 3-4 weeks before slowly, over the same 3-7 days, bring your specific gravity back up to 1.025, this will in effect kill all of the ich organisms on your fish, and if you have qt'd all of your fish, and basically qt'd your DT as well, you should, as long as you continue to QT all new additions, have no problem with ich in the future, this is a much safer, and much more effective approach than using rid-ich or any other brand of chemical.
just my .02