buy an RO unit off ebay for 89.95...you will be happy in the long-run
http://cgi.ebay.com/AQUA-AQUARIUM-10...QQcmdZViewItem

I bought one of these last year and now I have a perfect ph balance, week to week. I add calmag+ in order to re-introduce the proper concentration of minerals needed for optimum photosynthesis. hope this helps, good luck, keep us posted, lw