I have a BRS 150 gallon a day RODI system which I have added on a pump to increase the pressure. My RODI system consists of: pressure pump, 1 micron filter, carbon block, carbon block, 1 micron filter, two RO membranes, mixed bed DI resin canister then the second mixed bed DI resin canister. I have had it for about 6+ years and it works flawlessly. For salt, I use the HW-Marinemix Reefer Salt Mix from BRS. It dissolves fast without much precipitate and is a high quality and purity salt mix that approximates seawater. I've used it for several years and have great results with it. As others have said do a little research for which salt mix best fits what you want to do. If you do change salt mixes do it gradually so you don't change the water parameters too quickly. Marine life does not like fast changes to water chemistry! Happy Reefing!