Experienced reefers thoughts on supplementing CA and ALK?

[Original Fin]

It's my first reef tank, and I'm nearing the 9 month mark. I'm trying to decide on an ALK/CA supplementation method, and I'm hoping to get some feedback/advice from some experienced reefers. I'd like to shoot for a day to day stable/steady 9.6/429 (balanced). What supplementation methods can I use to get to that?
Over the last two weeks, I've measured the following daily avg. consumption rates for CA and Alk.

ALK .53 DKH/day (Averaged, Salifert)
CA 6.67 ppm/day (Averaged, API)
MG Holding at 1320, no measurable drop (Salifert)

This is more than what I expected considering how young the tank is, and how lightly stocked it is with mostly softies. Coraline growth is pretty extensive though. Besides the organisms that use CA and ALK, is there anything else that could cause both of these to drop so rapidly, or is this what you'd normally expect?

I change 10 gals every week using regular Instant Ocean and RODI (TDS 0). I preheat the RODI to 78 before mixing, and I run a powerhead for at least 24 hrs before using. I mix to 1.026 sg (Refractometer). It mixes to CA of 400 and Alk of 12.2, so I need to take that into consideration on change day. I estimate 65 system gallons.

I am dosing carbon (vodka) and I'm in the maintenance phase @ 2.2ml/day. Besides that, I don't regularly dose anything else.

I've experimented with Kalkwasser. I overshot ALK once with that method up to 16 DKH, but PH held at 8.4 with no obvious signs of trouble. ALK dropped back to sub12 in about a week.
I've recently used Baking Soda or Kent's Tech CB A to buffer Alk. I've also used the Kent's Tech CB B for CA. Here's the problem I'm having with that stuff: As a ballanced solution, the dosing instructions state you should dose equal parts of Alk and CA. That doesn't work for me because my ALK/CA aren't depleted in a ballanced way. It does go on to say that it's OK to dose them in different quantities...WTH???. Anyway, using this reef calculator 'Reef Chemistry Calculator FV' and plugging in my daily consumption, it says I need to dose 30.9 ml of part A per day, and 16.7 ml of part B. Each bottle is only 473 ml, and costs $12 ea. Two problems with that: 1st, I'll go broke with this method. 2nd, you're not supposed to dose more than 1/2 ml per gal of this product over a 12 hr period, which means I would need to split my daily dosage and do once in the morning and once in the evening...PITA. I'm aware that there are dosing pumps available, but I really don't want to go there just yet. Drip dosers, I don't think so. Alk would need to be set to drip .69 ML hourly, and CA would be 1.29 ml. I don't beleive they can be set that low.

Are there other methods I should be exploring? Is my math flawed?

TIA

[metalhead]

I think your math is sound Fin. The two part supplements are good, but expensive in some cases as you have found. I use seachem supps but dose the same way as any other two part. I can buy a pound of each for about 30 bucks which will mix about five gallons worth of each supplement. I think the problem you are having is caused by dosing alk and ca together. I never dose for both on the same day as I have found that they seem to cancel each other out. Don't worry about dosing equal amounts either, you should dose appropriate quantities of each based on your test levels, there will be some trial and error here until you get your depletion rates dialed in but it sounds like you're already on the right track there. Alot of others on here swear by the bulk reef supply supps and they are much more cost effective in the long run. Hope this helps.

[Original Fin]

Thanks Metal. I've been waffling on the large BRS 2 part kit with mag. I'm also looking for local suppliers for Peladow or Dowflake de icing calcium chloride. Read some Advanced aquarist articles about those being the most cost effective way to supplement CA. 50 lb bags are about $20. There's a swimming pool branded product that's the same thing.