Well, I had just boiled these (paranoid about whatever particles might have landed on them while sitting in the LFS). The guy at Nippon said to just boil them for a minute and rinse with saltwater. I suppose a small pod (the ones in my tank are miniscule) might have gotten inside, though the 'shell attack' happened within a few minutes of me putting the shells in.
My real queston, though, was regarding the empty shell as good excersize for his dactyls. BvM had been a renovating monster for a week or so, but he seems to have decided that the LR castle doesn't need any more windows at this point. Coupled with him not hunting down the hermits (I have found 2 snail shells in one corner, though...in the space of 3 days), I was just worried about keeping his smashers in good order.
I am a fussy mantis parent...
-Ron