I'm using RO water and it looks like I'm neglecting calcium when rebuilding my water. I'd rather add something I can measure to get the level to whatever it needs to be. Kent's liquid calcium and Seachem's reef calcium are sitting here in the house. Would either of these be suitable? If yes, what kind of dose/number of gallons would I want for freshwater? If not, what product would I want so I can measure the dose?