Circulating the water will increase it's gas exchange rate so I would circulate it as little as possible. I don't even circulate mine and it works just fine, cuts down on CO2 exchange once the crust forms etc. The way I do it, and I think how a lot of people do it is just to dump in the amount of kalk you want to use into your ATO container and just keep your pump a couple inches off the bottom of the container. Figure out about how much you evaporate per day and try and use that as a basis for how much you want to try dosing per day and then dissolve that much into the volume of your ATO container. I started out with like 1/4 tsp per gallon and just tested alk every day to see how that kept up and then just increased the amount of kalk I added for my next ATO batch and just used 2part to make up the dosing until you have the kalk dialed in.