Rock and Substrate

The foundation of any reef aquarium aquascape is its rock and substrate. Both are incredibly important not just to the appearance, but also to the health, of the system. Because they cannot easily be replaced after the tank is running and stocked with animals, it is crucial that the aquarist gets this part right the first time. To be clear, when we speak of reef rock, we are referring to the chunky calcium carbonate deposits of reef organisms such as coralline algae, clams, tube worms, sponges and (primarily) stony corals. The substrate is composed of the same, being formed from precipitates from the seawater and (primarily) eroded fragments of reef rock. Aquarists source reef rock from many places. It may range from totally natural (extracted from natural reefs and shipped wet as “live” rock) or totally artificial. In terms of cost, sustainability and safety (i.e. avoiding pests), the ideal choice is natural dry reef rock. It is natural (yet sustainable) because it is derived from ancient, extinct reefs. Because it is dry, it cannot carry unwanted organisms (aiptasia anemones, bristle worms, etc.) into your system. It is easily inoculated with beneficial bacteria and even coralline after it is placed in a newly set up and functioning aquarium. Much of the above applies to the substrate (be it sand, gravel, mud, or whatever). If a more naturalist look and function are desired, it is best to use courser grades in the main tank (to simulate turbulent areas such as reef bottoms) whereas a finer material should be used in refugia, especially those housing mangroves and/or seagrasses (to simulate calm areas such as estuaries). In this section, you will learn about hardscaping, the diverse flora and fauna that live on reef rock/substrate as well as how to seed dry reef rock.