They are both great imo, kalk is just easier. The only thing you would really have to test is ph and Mg, but the mg would be taken care of by water changes. Once you get your levels EXACTLY where you want them dosing kalk will pretty much keep them static. 2 tsp per gallon of RO/DI and only make enough to last a week. Have the ATO kick on about an hour after lights out, and it should help maintain your ph and Dkh through the night. Being that you have a small system, kalk is probably the easiest. Make sure the ph of the rodi with kalk is at 12.0 It may temporarily raise your ph above recommended levels if you run it during the day. It's so simple, but there are so many people that say otherwise. I had to try it myself before I was sold on it.