I have ultra alkaline, ultra hard well water. It has a ph somewhere between 8.2 and 8.6 I believe. Hardness and alkalinity, I am told, are off the chart (my local fish store).
You can imagine, not all plants and fish like that awful stuff. For one, my corydoras catfish can't stand it. Buying bottled water was getting tedious and a bit pricey.
Then I found the most fantastic article online for filtering hard alkaline water through peat. I just did it, it works so slick and easy, I'm kicking myself for not having tried this sooner! I just dropped my ph down to about 6.2 or 6.4 simply by pouring my water through my homemade peat filtering system. I'm currently slowly adding it by the cupful to my cory tank. They're loving this. (Going slowly with the change over the next few days.) I don't have a hardness and alkalinity test here at home - so that will have to wait until I take it to the fish store - but they probably dropped considerably too.
Here is the article that explains "How To"http://www.marksfish.me.uk/index.php?option=com_content&task=view&id=63
In his article, he needed large quantities - I only need several gallons at a time - so I used smaller tools. Instead of a bucket, I used an empty plastic drinking water bottle. Cut off the bottom, take off the cap, and you've made a funnel (turn it upside down). In the bottom of my funnel, I packed 2-3 somewhat packed inches of polyester fiber fill (sewing department at walmart - not treated with any chemicals). Then I put in 4+ inches of peat moss (bought at garden store - Schultz Sphagnum Peat Moss - no other ingredients - do not buy regular sphagnum moss, but sphagnum peat moss is just fine). The peat is bone dry - so you have to pour hot water through the filter you've just built first. This will help the peat get wet. Dump out the first (hot) water that you pour through or use it for your plants or lawn. After that, just keep pouring cool/cold/room temperature water through - and catch your soft water in a bucket, empty gallon water jug, etc. Check the ph vs your original water, and I think you'll be mightily impressed.
Hope this helps someone!