OK so I've been doing a lot of reading on various forums regarding integrating oyster shell into potting mix or using it as a top dressing for those species who benefit from it. I don't have any osyter shell, but I was at the beach today and picked up some various shells in the sand and water. Does anyone know if I could I crush them and use them in the same manor? (after rinsing the salt off of course!)? Is oyster shell superior? Thanks!