What should i buy to purify my water?

[megs_clark]

Hi, Im in need of advice again. lol. I noticed im getting some green hair algae on my crushed corol. I want to fix this before it gets out of controll. I have just a little right now. My tanks a few months old, 30 Gallon. I do 10% water change a week but am using tap water which i have prepared 7 days before each change. I only have live rock and a couple clowns, a brittle star, 2 turbo snails and 2 hermit crabs. SO im thinking i need to do something about the tap water. Im looking on JL Aquatics and my question. Should i buy the $50 water purafier (im thinking no) and if i need a more expencive one which brand, Aqua Fx or the Kent Brand. And do i need a R/O or should i just buck up the little extra and get the R/O D/I. Im planing on just ordering online since i live to far away from their so i cant go in and ask for advice. Any help on this would be great!! I check my water regulary with the saltwater master kit my api and my Nitrate Nitrite Amonia and Ph looks fine. I have not checked any thing else yet.