[tmz]

IME, constancy in alk is a key for calciifying corals like sps and lps;so, I would avoid bouncing it around;certainly not more than 1 dkh per day. When corals grow skeletal matrix and tissue , the process involves a number of elements including alk , phosphate and others ; raising or dropping alk quickly can knock it all out of balance if the other elements don't match up.
Generally increased alk will encourage more growth from calcifying organisms in an environment balanced for it but may occassion stn and/or burnt tips in one where other nutrients are very low. My advice is to pick a number for alk in your tank between 7 and 11 dkh ( personally, I like 8.5 for my system) and then do your best to keep it steady.