I too have the aga 180 with sps clams and others, with Mh. I have a CA reactor, and would never do without it. My Ca levels stay pretty constant between 480 and 500.
I wouldn't be looking for chemicals to buy, I would purchase test kits instead, and then buy the chemicals as you need them. I add Reefpure vitamin/HUFA supplement and Lugols plus on the weekends that I don't do water changes, and I find that my magnesium levels drop quite often, so I will add that as needed.
Along with your test kits, watch your corals for signs that things aren't going so well.
I'm still learning though, but my system is coming up on 2 years old, and most corals are growing, (except the gonipora) and none have died. My anemone has split 3 times.
HTH,
Mitch
[ September 18, 2001: Message edited by: Carpentersreef ]