The Biorock Process or mineral accretion is a technology used to grow structures and marine ecosystems in seawater. It provides a cost-effective and sustainable method to accelerate coral growth and increase coral survival particularly in areas where environmental stress has affected existing reefs. Biorock methods can help restore damaged coral reefs and provide building materials from sustainable energy resources for mariculture of corals, oysters, clams, lobsters and fish. When mixed with aggregates, accreted minerals can be used as building components on the sea bottom or on land.


In an attempt to slow the damage done to the world’s coral, artificial reefs have been built since the 1950s out of materials ranging from concrete blocks to discarded tires. However, most of these plans have failed to provide a new coral habitat, and one such artificial reef off the shore of Fort Lauderdale has become a complete environmental disaster. There have been some successes with artificial reefs, but most remain relatively barren compared with natural reefs. The one notable exception is the work of marine biologist Thomas J. Goreau and engineer/architect Wolf Hilbertz, who have been experimenting with a new type of artificial reef for over a decade.

The technology, elegant in its simplicity, is called Biorock. It arose from experiments in the 1970s when Hilbertz was studying how seashells and reefs grow, by passing electrical currents through sea water. What he found was that as the sea water electrolyzes, calcium carbonate (Aragonite) slowly forms around the cathode, eventually coating the electrode with a material as strong as concrete. Later experiments showed that the coatings could be grown at up to a thickness of 5cm per year. As long as the power is flowing, the structure would continue to get larger and stronger as time passed. It can also heal itself if damaged, something ordinary concrete can’t do.

Hilbertz’s original plan was to use this technology to grow low-cost structures in the ocean for developing countries, however his focus shifted to coral reefs after meeting a marine biologist. Because the Biorock process uses such simple materials, electrode forms can be constructed in a variety of shapes to mimic natural reefs. Because the calcium carbonate coating that forms is so similar to natural reef substrate, corals take to the Biorock reefs very readily. In fact, other experiments were conducted to see if the electrical current was harming the coral at all and the results were surprising; the coral actually thrived on the electrified reef.


Applying a low voltage electrical current (completely safe for swimmers and marine life) to a submerged conductive structure causes dissolved mineral crystals in seawater to precipitate and adhere to that structure. The result is a composite of limestone and brucite with mechanical strength similar to concrete. Derived from seawater, this material is similar to the composition of natural coral reefs and tropical sand beaches. Biorock structures can be built in any size or shape depending only on the physical makeup of the sea bottom, wave and current energies and construction materials. They are well suited for remote, third world sites where exotic building materials, construction equipment and highly skilled labor are non-existent.
GCRA methods provide a cost-effective way to increase coral survival from bleaching and disease, while restoring damaged reefs. In time, these structures cement themselves to the ocean bottom, providing a physical barrier that can protect coastlines from waves and currents that cause erosion. In the Maldives, during the 1998 warming, fewer than 5% of the natural reef corals survived. But on our GCRA reefs, 80% of corals not only survived, they flourished. Corals from these reefs are now recolonizing the surrounding natural habitats.

Constructing a new reef

To build a Biorock reef, an electrically conductive frame, often made from construction grade rebar or wire mesh, is welded together, submerged and anchored to the sea bottom. Sizes and configurations vary to fit the setting. Then a low voltage direct current is applied using an anode (power sources can include chargers, windmills, solar panels or tidal current generators). This initiates an electrolytic reaction causing mineral crystals naturally found in seawater, mainly calcium carbonate and magnesium hydroxide, to grow on the structure. Within days, the structure takes on a whitish hue as it becomes encrusted with precipitated minerals adding rigidity and strength. Electrical fields, plus the shade and protection offered by the metal/limestone frame, attract a wide range of colonizing marine life including fish, crabs, clams, octopus, lobster, and sea urchins. Once the reef structure is in place and minerals begin to coat the surface, the next phase of reef construction begins. Divers transplant coral fragments from other reefs and attach them to the ark’s frame. Immediately, these coral pieces begin to bond to the accreted mineral substrate and start to grow—typically three to five times faster than normal. Soon the reef takes on the appearance and utility of a natural reef ecosystem rather than a man-made one.

Due to electrolysis, corals on ark reefs gain energy affecting growth, reproduction and their ability to resist environmental stress. These reefs grow rapidly and get stronger as they age. And unlike some other types of artificial reefs made from cars or tires for example, Biorock reefs don't leach harmful pollutants into the sea.

The Biorock Process is the only known technology that can sustain corals through warming water temperatures.
*Coral species typically found on healthy reefs gain a major advantage over the weedy organisms that often overgrow them on reefs stressed by eutrophication. In tests where the electrical current is interrupted, mineral accretion stops and weeds begin to cover the corals. But, if the current is maintained, coral reef habitats can often be restored even in areas where water quality would prevent their recovery by any other method.
*Biorock structures have unlimited potential for making breakwaters that actually get stronger with age. If waves or colliding ships cause damage, renewed mineral accretion makes them, to an extent, self-repairing.

As of 2008, Biorock coral reef projects exist in over 15 countries (and mainly in Maldives, Seychelles, Thailand, Indonesia, Papua New Guinea, Mexico, Panama and, in one of the most remote and unexplored reef areas of the world, Saya de Malha Banks in the Indian Ocean and represent the only restoration method known that can sustain and grow natural coral species using only basic elements. These incredible structures not only grow with time but also assist damaged coral in healing while increasing growth rates up to 5 times faster than normal.


* Hilbertz, W. H, "Toward Cybertecture",Progressive Architecture, May 1970
* Hilbertz, W. H, et al, "Electrodeposition of Minerals in Sea Water: Experiments and Applications", IEEE, Journal of Oceanic Engineering, Vol. 4, No. 3, pp. 94-113, July 1979

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