Hi Jojoe, to be honest I do not use oyster shells a lot with my succulents, with the exception of one baby Crassula ovata Gollum and some sedum rubrotinctum container where I used a half shelf as support and decor. So far I have not seen any adverse effect.
I think I have read in our semp threads here that they use grit in their mix, so they may be able to answer your question much better.
For what its worth, here is my Crassula ovata 'Gollum' and Sedum rubrotinctum container, I do not have definite percentage of how much I mix stuff, I just eyeball it and feel the soil
26Mar2013
05Mar2014
