I take a teaspoon of kalk and mix it with a small amount of fresh water, maybe a quarter cup. I mix it up, and then let it settle for a few minutes. This works best with powerheads and pumps off. I use a syringe with a large diameter needle. You could also use one of the plastic tipped syringes in the Salifert Kits. Using the syringe, draw up as much thick liquid talk from the bottom of the mixed kalk. It will be a little thick, but not really a paste. Gently dispense the kalk over the aiptasia, being careful not to have any of the kalk touch your corals. If some is floating towards your corals, mix the water so as to disperse it in the water. Let it sit on the aiptasia for a few minutes. The aiptasia will shrink and shrivel. I like to remove the kalk to avoid it touching other corals, so I use an airline and suck out the kalk and dissolved aiptasia into a bucket to toss. Turn the pumps back on, and you should be good to go. I hope that is thorough enough.
