Objective: To maintain your garbage disposal

Which of the following solutions is more sound in terms of naive physics reasoning?

Pick from:
(a). once a month grind about about a dozen ice cubes. The ice will sharpen your blades and eliminate any grease trapped in the drain.
(b). once a month grind about about a dozen small rocks. The rocks will sharpen your blades and eliminate any grease trapped in the drain.
(a).