If there's even the tinyest piece of sand or coralline still attached, they should stick easy. Try to scrape something off with your blade as you frag them. If there's nothing attached, just barely polyps nothing, you can still make it work with lots of glue. They'll be ****ed off for a while and some may not make it. Only time I've had it not work at all, the zoas were so traumatized to begin with, they just kept slimming up and sloughing off, and eventually died.
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