marine safe rock?

bucket of salt water for a week and then put a cleaner shrimp in it if it lives a week them it is likely OK but no guaranty on that because it could take a while for a reaction to happen.
Bill

[Reef Puffer]

thanks guys!

[monocus]

could be lace rock(if it's heavy) or pumice-the froth from a volcano(if it's light).remember almost all of b.c. use to be ocean floor at one time.take it to a local high school teacher-they might be able to identify it better