[dukes707]

i agree with Gasman059 about the sps holy trinity being cal/alk/Mg. they all share a relationship, although nonlinear in some cases, all are relative to eachother in respect to keeping things stable. all should be tested and kept as stable as possible.
i use kalkwasser in an ATO for all top off water. pH stays rock solid @ 8.2. i recently got through a bout with wack alk due to a faulty salifert kit i had and my Mg was off by a large margin due to using only kalk as my cal/alk additive. i wasent aware of the amount of Mg depletion that occurs with using only kalk, and i paid for it. and got an API for alk.
thanks to randy's informative articles on mg and kalk i was able to remedy the situation before losing too many sps'. some are still recovering from the subsequent brown out. my alk fell to about <6 but after correcting my mag levels with randys two part #3 mag supplement mix and supplementing with some bakng soda after about a lil over a week things are finally getting back to relative normal.
word to the wise, whatever supplementation system you use make sure you understand it completely, pros and cons. read as much as you can on whatever system you are using.
now that things are stable again, and polishing waterchange water with Mg additive prior to changing things are rock solid.
cal~400 alk~8.5 mg~1350 pH-8.2 steady. i like to ry to keep things as close to NSW, and my critters seem to appreciate it more than keeping things supersaturated and at the high end of the params. my experience with my system and what supps i use.