New to RO/DI water use

[salty210]

I have a 210 gal FOWLR that has been running for over a year now. I finaly got tired of the all day water change. You know 8 hours making water with one of those tap water filters and a 40 gallon big brute trash bin.
I am lucky enough to have a spot, somewhat close to water, a drain, and the tank, that I could build a water prep area. And with a flick of a switch, my water change is done. Well, its not quite that easy ,but it has saved me hours of watching water flow, and the occasional wet floor.
So what I need to know, are there any additives I should be adding to my new ro/di water?
I use IO salt and I know that it is a little low in ca and mg, probably why I'm not getting good coraline growth. I,d like to pay more attention to those levels also. What should I use? Liquid or a powder buffer and what kind.
Thanks.