It depends on what your budget is. Cal Prime gives 10% more Ca, which is the engine for plant metabolism. Regular cal nit works and is cheap.Sorry, I was referring to Jack's part B Cal Nit. I would prefer to stay with RO water so I know what is going to my plants. I know you have to add cal mag with RO water, so what would be a better option, the Hafia Cal Prime or Jack's Cal Nit?