I'm still planning my aquarium setup but one thing I've wanted since the beginning was to use Shells I got form my honeymoon to make a "reef." What I have is a bunch of large(larger than your hand) broken spiral shells that have basically turned to rock. I don't think their fakes shells, as they have a complete spirals all the way through and most fakes don't. These have either been covered in silt for a long long time or on the beach covered in sand for a long long time as they're basically petrified shells. What I need to know is whether or not they'll be safe for using in an aquarium, and if so how I can properly sanitize them. They've been in a box for a year now(our honeymoon was a year ago) and I've rinsed out all the sand. I also have a a small bag full or sand/broken tiny shells and was wondering if that work mixed in with gravel for a more natural look. Any help/tips would be appreciated. I've got alot of planning to do.