Yup just like above. The vinegar is an acid, and if the lannon stones are carbonate based, they will foam since the acid will eat at the calcium carbonate based rock. If you put carbonate based rock (aka limestone) in your fish tank, it disolves and can increse the hardness and pH of your fishtank. You don't want anything to disolve in your tank.
You can boil the rocks, scrub them really well under the hot running tap. Some people will also soak them in a mild bleach solution then soak them in a dechlorinated water. You just want to make sure you wash all the yucky yard stuff off.
~~Colesea
