I am trying to find out how people are mixing their own saltwater. What I have done in the past was just mix it in 5 gal buckets for my water changes. What I want to do is make a whole automatic system with reserve tanks (55 gallon plastic drums), RO/DI system, and a top off tank. My questions are what items, additives, and other items. If you have designs please explain how your system is setup.