Clean water from our tap

I've been struggling with providing an environment where invertebrates can live happily. My experience so far, not so good. Snails die, anemones die. Fish thrive, hermit crabs are doing well.

Water quality seems okay, but with the inverts not happy, my habitat is limited.

In an effort to address the incoming water quality issue I have researched and found two camps: Clean via Reverse Osmosis systems which are costly, or some other method. I don't want to dive in to the R.O. world just yet, since those systems can run in to the hundreds, so I am left with another option that seems promising:

Mechanical/chemical filter processes ala "Britta". Happily, I found a source for a DIY solution that may be just the ticket. In a nutshell this approach basically has you build from PVC and filter media a large scale "Britta-Like" filter.

Here's the link: Make your own marine-grade water filter. And here is a link to the recommended polymer pad manufacturers' site

I'll let you know how it goes.