Does it have to absolutely be submersible? The cool thing about using a pump like an AquaLifter is that it pumps slowly. I just added Kalk into my ATO yesterday, and I didn't have to change anything about the setup. The AquaLifter pumps slow enough that I don't spike the tank when my ATO kicks on. My ATO is set to activate every three hours. It's cuts on for an average of 30 seconds each time.