How big is your tank? If you change a gallon of the dirtiest water from the bottom of the tank every week in a 10 gallon tank then I would say you have a pretty ogod water change schedule.
Ich is treated several ways, and there have been a lot of threads on here about it. Search through the archived threads using the
Search page and enter:
ich
or
ich; scaleless
in the search box . I posted a thread a while back about how to treat ich in a tank with scaless fish, shrimp, and live plants, a tough challenge. Some stand by something called Kordon+, some stand by the salt and heat method. Either way, it'll likely take a couple weeks to get rid of it.
Nobody ever thinks it will happen to them, but that's what happens when we don't use protection. If you don't have a QT, you are sure to get ich, again, and again, and again. It will just keep getting reintroduced to your tank from new fish.
Read
this, it is my thread from a couple months ago about ich with scaleless fish:
http://www.myfishtank.net/forum/showthread.php?t=25961