Maybe you could kalk the aptasia outside the tank? In a small bowl?
That would work well, hadn't thought of that. Wish I hadn't glued the zoas directly to the rockwork and they have since grown even more onto the rocks. I really should have taken care of these earlier.
Maybe I can use some kalk paste before a water change, or heat up the lemon juice. I read hot water can kill them sometimes too.
I'll get some pics soon! Kept the lights of all day today. Read about another reefer who knows a lot of zoas doing it every month and figured it wouldn't hurt.