The Berkley has a optional fluoride filter, but there’s no fluoride in rainwater, so you shouldn’t need it.
In my experience, filters are the places all the nasty stuff grows, as they have (especially activated carbon) lots and lots of surface area for the biofilms to grow on). As Steve pointed out, rainwater needs treatment to make sure it’s potable, but there’s no fluoride in it. My first-line rainwater treatment is http://tripleo.com/ systems running in a concrete cistern. We’ll be implementing another one early this year as a replacement for buying bottled water for an island community, with something like a 2-year payback!
That’s a good pint about having to remove the aluminum afterwards and stuff growing on it. Looking at the site you posted and I’m still wondering how much in terms of minerals and other stuff such a filter would remove. I do realize that off course rain water doesn’t have fluoride. But I’m using tap water. I don’t collect rain water, i just thought that there might be someone knowledgeable on the matter on this forum.
The ozone/filter units don’t pull out any dissolved minerals or chemicals, but they do sterilize the water and filter out the bigger particles. They also make some chemical change to hard water to soften it, though I don’t understand the details. While you could fill a cistern with tap water and treat it with ozone, (and I’d love to do just that with my well water), there are much more efficient ways of treating tap water.
You can get filters for any micron rating you want (I’ve seen 0.1 micron), including ultrafiltration and (at the extreme) reverse osmosis. The problem with prefiltering is that rain tends to come in bursts, so you need something to store the water in while you are prefiltering it into your active cistern. The Racor filter does 3 or 6 GPM, and the water comes off my roof at something like