Hello, and welcome to the forum!!
My first suggestion is that you post a complete set of numbers, including FC and either TC or CC; pH, TA, CYA, and metals. You can get those printed out from the pool store. They will help us give you good, useable, accurate advice. However, STOP buying the stuff they're selling you! Throwing stuff at the pool is going to make your situation worse, instead of better. In the meantime, if you can get a good drop-based kit and do your own testing, it will save you hundreds in money, time, and aggravation. The Taylor K-2006 is the one we recommend, and can be ordered online several places but the best two prices I've seen are at http://www.amatoind.com or at http://www.spspools-spas.com. WalMart sells a 6-way drop-based kit for about $15 that can be used in the meantime, but with iron in your water, you're gonna have to be very careful about not getting lazy and keeping your chems in check.
The really simple answer to your question is that the metals in the water are going to have to be "bound" by a sequestrant for the lifetime of your pool. The metals don't filter out; rather, it's a matter of keeping them in solution in the water to keep them from "dropping out" and causing staining. This is going to require re-applications of a sequestrant on a regular basis, and is also going to require tight control over your Chlorine and pH levels to keep your pool from staining.
Marie (mbar) is our resident metals and stains expert, and I'm sure she'll be along soon to give you specific answers to your questions, but in the meantime I'd like to encourage you to take some time and read some of the threads in the metals forum to get an idea of what you're dealing with in terms of maintenance. Also, take a look at this thread where Marie talks about Ascorbic acid treatments to remove staining. Although this doesn't directly apply to you at this particular time, the latter part of the post does discuss pool water maintenance with metals and may help you understand what's required to keep it looking good.
Janet
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