If they are on their own rocks, and not on a base rock that you can't remove, I would remove the coral and cut the aiptasia off with some coral cutters, or even a flathead and a hammer.
Reason I say that is peppermint shrimp can't always be trusted. They are very opportunistic and might start tasting your corals. I would go with manual removal first unless you have no other choice and can't remove the rocks with the aips.
Split it in half, cut the aip off, then glue both rocks back together. Zoas will cover whatever you put them on, and before you know it, it will be one colony again.
Speaking of nutrients I can't seem to get my salinity higher than 21 and my alkalinity doesn't go higher than 7 no matter how much I drip it. What can I do? Haha