No, a rock itself cannot be alive, and certainly does not move on its own. Live Rock (“LR“) for a marine aquarium by definition, is a mixture of a hard rock made up of calcium carbonate skeletons of long dead corals, or other calcareous organisms, with an assemblage of diverse living micro and macroscopic marine organisms on, in and amongst it.

LR plays a primary important role in a marine aquarium, as part of a crucial resource in keeping almost all livestock. LR can act as main biological nitrification base or biological filter in a marine aquarium, while enhancing the aesthetic appearance of the reef aquarium and providing shelters for many inhabitants.

LR immediately introduces bacteria, numerous algae, and small invertebrates into an aquarium, contributing to the overall quality of the aquarium water. LR offers more surface area for bacteria to grow than a trickle filter to handle significant bio-load of fishes and invertebrates.  Waste products from livestock such as ammonia, nitrate and phosphate are handled by LR in different manners.  Ammonia, nitrate and phosphate are readily assimilated by the many species of algaes and photosynthetic corals growing in and on the rock. Ammonia are quickly converted into nitrite and subsequently nitrate by the bacteria. Nitrate will either be absorbed by the algae and corals as their nutrient, or it can be denitrified by denitrifying bacteria in close proximity to the nitrate producing nitrifying bacteria.

Despite the wonders that LR can perform, LR should be quarantined in a new reef tank for a period of two to four weeks. This period is known as the “curing period” which allows observation and stabilization in order to reduce any potential pest and parasitic organisms, and to allow good cycling of initial ammonia, nitrite and nitrate spikes. Once the LR is cured, it can be an amazing complex living filter of all kinds.

Now, who would want a Dead Rock for their reef aquarium?