this subject is very interesting, there is a lot of controversy but from what i understand and what i have seen by installing 3 systems and having a fellow reefer friend that works in this RO and filtering field i have come to the following conclusions:
IMO and IME needing 0 PPM for me is not necessary, Living in TJ Mexico the water from the street comes at 750 to 1000 PPM so one of my best system gets it down to 45 (without resin) and another system i have gets the water to 100 PPM, all of wich (even 150 ppm) are still consideret potable/drinking water without any risks, infact i have even tested drinking bottled water and has the same 40 to 130 ppm ratio with some exceptions.
i have had my tanks running for a couple of years with 100+ ppm drinking, purified, distilled and RO water ass top off and as salt mix with no issues what so ever, i have also used (currently) salt water for WC, and the system i got for my house recently does 35 ppm, wich im very happy but would be an issue for me at higher ppm. also, my friend and i have built systems with a mix of filter housings and different fittings, all that matter in the end is whats inside of the plastic cases, the membranes, the filters etc. having said that the last system i got was bought not built and i got it for a good price, i needed a kit with a booster pump and i wanted UV so you have 2 options, there is a sponsor wich has good systems and the link is
Aquarium Water | Reverse Osmosis | RODI Water | ReefKeeper Water | Products and answers for your water treatment needs., or i have found this seller on ebay
eBay My World - h2osplash that has prebuilt systems with decent and quality parts, i was a little unsure as to purchase this systems on ebay but i didnt regret it i can tell you. i have purchased from both and they are both very good working systems.
i would suggest you get one that has a pressurized tank for storage, they are 3.5 gallons usually, so if anything happens you have a little water stored for an emergency.
