I've got a few ideas and I'm sure most should be eliminated, so here goes:
I'm trying to get my GH down around 6, I'm setting up a CO2 injected 100 gal tank, still not sure what biotope, although I'm seriously considering Travis' African Mbuna setup since my water is already so hard. I've got a small 10GPD RO that I could tap into for weekly changes but was hoping I could cut my GH down by using water from our in-home water softener (one of those Sears Resin-bed softeners that use the salt pellets). It would be much easier if I could go this route (and cheaper too w/ a lot less waste water) and it would retain my KH around 6. Just wanted to know if this is possible or if the water from the softener contains other by-products that will harm the plants & fish.