Need a happy home for your clam to grow and live? Our clam rocks are made from our Ancient Reef Rock, dry aquarium reef rock that has been harvested from the Earth locally, near our South Florida home. We've carved out an opening for your clam to rest comfortably in, and pressure washed the clam rock so it is tank ready. Choose from three available sizes, small, medium, and large. For tank planning/placement purposes a small clam rock will be approximately 6 inches long, medium approximately 9 inches long, and large approximately 12 inches long.