I purchase the pickling lime online. I use it to make limewater (Kallawaser) for my ATO water. I got 6lbs for $24 at Walmart.
The product I get is Ms. Wages Pickling Lime. Places like Walmart and Fry's use to carry it in the stores, but I haven't seen it there lately. It is used to make oickles so there might be a local store near you that carries it. If you can't find it let me know I will be at the Frag-O-Ween meeting this Saturday. I can bring you some.
I found a recipe for it online, but basically I use 2 tablespoons and mix in enough DI water to make a slurry. I was able to get a syringe with a metal tip from my vet. I stab the Aptasia and inject it with the slurry. The slurry needs to be thin enough to squirt out the small hole in the syringe. I store the unused slurry in a plastic container in a cabinet and use it as needed. I only use a small amount in the syringe and discard what I don't use.