If I were to purchase a water filtration unit, I will most likely go with just a DI unit, rather than RO. I think it would serve my purposes fine. However, you have to use muriatic acid and lye to recharge some filters, which from what I have read online are dangerous chemicals and thus, I am apprehensive about using them. From reading a lot at wetwebmedia.com, I think a DI unit will work fine. It's not a reef tank, only fish only. However, I am interested in hearing if anyone has tried the DIY tap water filter with poly-filter pads. Also, if anyone has any DIY plans for an RO/DI or just a DI unit, it would be greatly appreciated. I have found a few articles about DIY water filtration, but no solid plans.