I use Mrs. Wages Pickling Lime [5.00 for 2 lbs] dumped quite inaccurately [about a pound at a time] into a 32 g Brute can/ATO reservoir, with a maxijet 1200 topoff pump throttled down to a locline hose. A piece of lighting grid just slightly larger than the bottom holds my pump out of the 'soup' down below, and it gets stirred only when I add more ro/di to the ATO.
It costs practically nothing, since I was already using the ATO, and does not glitch-up. Mrs. Wages is cheap, compared to Kent Turbo Calcium.
I do have to test for and supplement magnesium: my consumption is not huge. [54g display, 30g sump].
In my correspondence I have noted that 120g is about the upper end for relying solely on kalkwasser for supplementation...and that gets edgy, too, depending on evaporation---because, of course, an ATO only doses when evaporation calls for it; and because you cannot easily 'force' more calcium into the topoff than that 2 tsp saturation. [There is a method of doing so, involving vinegar.]
Usually when you outstrip the needs of a kalk drip, a calcium reactor alone will do it; but some people run kalk AS WELL AS a calcium reactor, because of ph issues in their particular tank.
I found that calcium demand chugged along for about 3 months at 1/2 tsp a day for my stony tank, when first set up, then soared to 2 tsp a day of Kent Turbo Calcium all in one week. WHen corals start to grow, they start sucking up calcium bigtime, and in my tank, they all hit the same point together. Maybe one touches off the other, who knows? Or it was just tank conditions.
Mistakes [massive overdoses/topoff accidents] are pretty common with new kalk users, but rarely do any damage. What happens---the ph soars for a few hours, and then starts to drop. You can dose a little bar soda water to hurry that drop along, but you don't want to overdo it, or you can overshoot the dose and have trouble in the other direction. Overdose with a calcium reactor seems to be more serious.