I honestly don't know. It all depends on how much coralline you want. Here's what I'd do if I was in your shoes...
Get your Ca
up to 400, or wherever you want it, using TurboCa. Don't increase your tank's Ca
levels more than 20ppm per day. (That's just want the back of the B-Ionic bottle says... seems like it's a good limit.)
Once at that level, don't add any Ca
for a week. After a week, measure your Ca
level again and compare. With your results, you'll be able to know how much Ca
/day your tank is using. Use that calculator cccapt linked to, and figure out how much of whatever Ca
supplement you want to use you need to dose per day to keep your levels stable during the week.
If you don't see any drop in Ca
over the week, then don't add anything. Yet. But keep testing each week. Eventually, as you coralline builds up, it'll start chewing up some of that calcium and you'll see a drop. The brain will probably take a little, much not much right away. It's probably going to devote it's energy for the next few months in getting used to its new home!
I dose 20ml of Part A & B of C-balance per day. That, in addition to adding enough TurboCa to my PWC
water to bring it up to 400ppm calcium, my tank stays consistently at 400ppm calcium and between 8-9 dKh
alkalinity. Magnesium stays between 1140 and 1200ppm.
Personally, if I were to leave for three days, I'd just not worry about it and see where I'm at when I get back, and play catch up if I have to. That's not long enough to really cause a problem. Even if you have a calcium hog of a tank.