I am looking into getting a RO system but it is all cery confusing. There are so many brands that look alike. I am thinking about getting Captive Purity 35 GPD Deluxe RO Filter System but i dont know if I have to get a DI canister. I have always had a slight Nitrate problem and can never get it below 20 ppm. I dont have any sps or $500 fish so the water doesnt need to be "perfect" just as good as possible. So my question is, what is the best RO system (id perfer not to go over $200) and do I need DI, Thanks