It's not the end of the world. If you have some sort of star-crossed attachment to the rock :biggrin:, then simply soak it in a Muriatic acid solution (1 part acid to 1 part water) until the fizzing stops. Then, it would be fine for aquarium use.able_ranui said:Well, I tested it with vinegar in several spots and ONE spot fizzed. So I guess it is not aquarium friendly. I'll have to find another rock I guess.