This is all good advice, although I would do things in a slightly different order. First of all, I would start using kalk as soon as normal WC's become insufficient, and continue to use it, even if/when you start using a two part solution(s). It's a perfect balance of both Ca and alk, and will utilize some of the CO2 in your system to help keep your pH up. There are a few different delivery methods you might consider, including: ATO, dosing pump, and a simple gravity drip. Its shortcoming is the fact that you are limited as to how much you can add to your RO/DI water (2 tsp./gal.), and your evaporation rate.
Secondly I would start with a DIY 2 part, since its about as simple as you can get to make, and is a lot less expensive. I just did a cost analysis on another site, I'll past here:
1 gallon of Calcium Chloride is $17.09 @ BRS. Using recipe #2 it yields about 14 gallons of solution which works out to $1.20 per gallon.
12 lbs of A&H Baking Soda is $7.57 @ Walmart. Using recipe #2 it yields about 14 gallons of solution which works out to $ .54 per gallon.
DIY total for both parts = $ 1.74
So, Br******** - buy Parts A&B for $53.76 (Sold in 2L bottles @ $13.89ea. = .21 per oz. = $26.88 per gal. of each part = total of $53.76)
Saving $ 52.02
Recipe #1 might be twice as expensive, so say at most $ 3.48.
Saving $ 50.28
Test for Ca and Alk, and after you've made/bought your solution, I would add whatever you need to get to your desired parameters, i.e. Ca @ 420, Alk @ 8, etc. using
this calculator. Once your parameters are where you want them, start testing each day and see what your demand is. Since you're at a point where your WC's aren't keeping up with your demand, I would start using kalk @ 1 tsp. per gal. of RO/DI and ultimately go to 2 tsp. per gallon. Once your demand exceeds what your kalk is providing, start the two part, again use the calculator to determine the daily dosage.
