Chairs = common noun; Roll-O-Rocker = proper noun. Harriet threw the stale cucumber sandwich in the trash can and fantasized about a Big Mac dripping with special sauce. Sandwich = common noun; Big Mac = proper noun. Because we like an attentive waiter, we always ask for Simon when we eat at Mama Rizzoli's Pizzeria.
Answer: Reef Sand is live sand when it is on the bottom of the ocean floor, it is here where the reef sand is alive. When the Reef Sand has been out of the seawater for a period of time and exposed to the airborne elements it is considered to be dead sand. (lacking nitrifying bacteria).
Coral reef. Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals. Coral reefs are built by colonies of tiny animals found in marine water that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps belong to a group of animals known as Cnidaria, which also includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons which support and protect the coral polyps.