Kalk is pretty easy to use and will support both alk and pH. I prefer a small reactor fed by an ATO system but some people just add the kalk powder directly to their ATO reservoir.
If you're considering dosing two-part, I'd recommend getting a doser sooner rather than later. Many small doses per day is smoother for your livestock and less work for you than manual dosing, especially as you get some SPS growing. To figure out your alk consumption and thereby your starting dose, first measure your alk carefully and note the time. Now measure it again over the next few days, at the same time (no water changes or additives.) It may stay the same or slightly decrease. Wait longer if you don't see a definite decrease right away. When you do, take the drop in alk measurement, divide that by the total number of days, convert that result to mEq/l if necessary (= dKH/2.79 ), and multiply by the volume of water in your tank in liters (= gallons x 3.785 ). This number is your mEq alk consumption per day. Most alk products have their concentration listed on the bottle in mEq/l. Take your number and divide by their number, and that will tell you how many liters of their alk you need per day to maintain alk based on current consumption. This is a good starting point.
Or, you can just follow the product's instructions for starting dose, and adjust your subsequent dosing based on measurements. This works fine for the most, especially when you're just starting with sps, and involves much less calculation.
Also, I'd suggest doing smaller water changes. I also use RSCP, but never more than 5%, with water taken from the dt and returned to the sump, with the return pump running. Coral Pro is potent stuff .
