This. You're better off with two part and a doser but kalk in ato will work. Worst part is it tends to swing your PH a bit too much as the ATO adds a fair amount each time it kicks on. You can run amazing systems off of just kalk but it's better to drip it 24/7I don’t see why not, maybe start lower concentration of kalk solution, such as 1 teaspoon per gallon of RODI. I am still using kalk solution with my ATO and I supplement it with daily dosing of 2 parts (my tank is heavy sps), but I started with just kalk solution then gradually increase as the Ca and Alk uptake in my tank increased