Hehe. Bioling only doesn't hurt if doesn't *crack* the item you're boiling!!!!! Make sure to increase the water temp slowly so that the shells don't split.
I'd advise using bleach. Remarkably, this stuff has little effect on fish if used to clean ornaments/plants. I'd advise dropping the shells in a 10-20% bleach/water solution and leaving them for a 10 minute stretch or a little longer. Afterwards, wash *thoroughly* and make sure no bleach is left in the inner recesses of the shell. At this point, I'd think they're ready for your Lamprologus spp!!!
Bleach isn't an acidic solution, so it shouldn't cause your shells to fizz away, but check to be sure that there's no chemical reaction taking place! Keep an eye on the shells after you've added them to the bleach solution. Good on your partner for getting those shells for you!! Get some pictures of the shells up if you can.
I've got some fantastic shells that I picked up in Baja California (probably illegally now that I think of it, but I'm not sure of that...). I will certainly use them in the future for my Lamprologus, Neolamprologus spp. *when I get them...* And I will get them!