While you cannot spontaneously generate coral from dry rock alone, dry rock serves as an excellent and widely used base (substrate) upon which coral can be grown in a properly maintained reef tank environment. Coral, being an animal, needs to be introduced and attached to a surface like dry rock to begin its growth process.
Understanding Coral Growth
Coral polyps are tiny animals that live in colonies. They grow by budding new polyps, which over time, form the complex structures we recognize as coral. For this growth to occur, coral needs a stable surface to attach to and specific environmental conditions, including:
- Appropriate lighting
- Proper water flow
- Stable water parameters (temperature, salinity, alkalinity, calcium, magnesium, etc.)
- Sources of nutrition (either photosynthetic or captured from the water)
Dry rock provides this necessary stable surface.
The Role of Dry Rock in Reef Aquariums
Dry rock is essentially calcium carbonate rock that has been harvested, dried, and is free of existing marine life. When placed in a saltwater aquarium and properly cycled, it becomes the foundation for a captive reef ecosystem. Over time, beneficial bacteria, algae, and microfauna will colonize the porous surface of the dry rock, transforming it into what is often referred to as 'live rock'.
Colonization of Dry Rock
One beneficial organism that commonly colonizes dry rock in a reef tank is coralline algae. While different from coral, its growth is often seen as a sign of a healthy, mature system and can aid in calcium/alkalinity stability, which benefits coral.
According to one reference on the topic:
Will coralline algae grow on dry rock? Absolutely, as long as you add an initial source like a bit that comes in on the bottom of a coral or on a single piece of live rock from an established tank that you trust.
This means that even dry rock can become covered in desirable pink, purple, and red coralline algae over time if spores or fragments from an existing source are introduced into the tank. The reference also notes that you can speed the process up a bit by scraping it off a rock allowing it to spread around quicker. This highlights that dry rock is a receptive surface for calcifying organisms in the right conditions.
Growing Coral On Dry Rock
The process of growing coral on dry rock involves:
- Acquiring Dry Rock: Choose porous dry rock suitable for aquascaping.
- Cycling the Tank: Place the dry rock in your aquarium filled with saltwater and cycle the tank to establish beneficial bacteria colonies, making it a suitable environment for life.
- Attaching Coral Frags: Obtain healthy coral fragments (frags) from a reputable source. Use aquarium-safe glue, epoxy, or putty to attach the frag securely to the dry rock.
- Maintaining Tank Conditions: Ensure your aquarium has the correct lighting, water flow, and stable water chemistry required by the specific type of coral you are growing.
- Growth: Over time, the coral polyps will grow and encrust onto the dry rock, becoming a permanent part of your aquascape.
Using dry rock allows hobbyists to build their aquascape from scratch and control the introduction of organisms into the tank, providing a clean and stable foundation for long-term coral growth.
In summary, while dry rock itself doesn't generate coral, it is an essential and effective substrate used to support and grow coral fragments in a thriving reef aquarium environment.
