What Is Biorock?

Biorock is a novel technology to create an artificial coral reef. We’ve been building steel structures and attaching a low voltage of direct current through when installed to create accelerated growth of corals, with increased resistance to climate change, coral bleaching and increased storm activity.

Reef gardeners and Biorock students recover corals that have been dislodged from the reef in storms, anchor damage or poor tourist behaviour and transplant them carefully on the structures.

The low voltage current creates an electrolytic reaction and a stable substrate of calcium carbonate accretes onto the rebar causing the structure to grow in size and become heavier and anchor itself to the reef. Layers of calcium carbonate are deposited on the structures, providing a sturdy and optimal surface for corals to cement to. The low electric current also promotes the coral to grow faster and stronger than on the natural reef.

Doing this, the Gili Eco Trust has managed to restore some of the beautiful coral reefs of Trawangan in a short period. They have proven to be more resilient than natural reefs in severe bleaching events of 2009, 2010 and 2016. More than 150 structures are placed in the waters around the Gili Islands, fostering a lot of new corals and a vast array of fish life.


Coral reefs are endangered by many different factors, both natural and caused by human influence. 

Worldwide about 10% of all coral reefs have been destroyed, while 75% is threatened by human interaction. With help from coral restoration and Biorock technology in the Gili Islands, more corals will survive these threats, sustaining life underwater and providing oxygen and protecting beaches from coastal erosion.

The Gili Islands, whilst now safe from destructive fishing methods such as dynamite and cyanide fishing, still are battling with many threats that affect our beautiful marine ecosystem. 

Anchors, although widely unaccepted and illegal in Gilis, are still used for unregistered snorkel tours and import boats in certain parts of the islands. It is very apparent in these areas the destruction caused underwater, the damaged reefs are now sites of rubble, quickly overcome with algae. Whilst the Biorock structures do not create wholly natural reefs, they work fast to mitigate damage in destroyed areas of reef and start to stabilize loose sediment and rubble that was previously barren.

We have also increasingly observed mass bleaching events on some or all of our dive sites around the Gilis. Major events that affected Gilis corals to date were 1998, 2009, 2010 and most recent and severe, 2016. Whilst all reefs including the Biorock reefs were at least partially bleached, studies carried out during the 2016 Il Nino event on corals transplanted onto Biorocks had a slower rate of bleaching than on natural reefs, and also when the sea cooled back down (3 months later) they had a much quicker recovery rate and overall lower mortality rate.

With events such as these, accelerated in frequency and severity by the climate crisis, it is critical to keep up the maintenance of the Biorock structures to protect our reefs from further damage.

Powering Biorock with renewable energy

Currently (no pun intended) the main disadvantage to Biorock technology for restoring coral reefs is that it uses DC electricity from the island and the main power grid. Not only is this powered by finite fuels such as oil and petroleum, the island gets frequent power cuts. Our initial solution to this was to install floating solar panels above some of the Biorock structures to power them throughout the day using the sun, letting the corals rest, feed and grow naturally at night. This has proven effective however creates a slightly slower growth rate of the coral species. We currently power 35 Biorocks in this way.

Our latest strategy is to be able to harness energy from what the Gili Islands are most famous for, our ocean currents! This is an almost infinite source of energy, flowing through the channels and coral reefs daily. We have partnered with Dynorotor who are looking to create custom energy generation from reversible ocean currents that can be affixed directly on, or nearby to the Biorock sites to create power from the ocean to continue the electrolytic reactions.




We run a two-week intensive coral reef restoration program at Trawangan Dive centre. During the course, you learn extensive marine ecology, substrate identification and complete training for the Reef Check Eco Diver. Assessing the health of natural reefs around the Gili Islands using transect surveys and collecting data to complement long term data on reef health. The second week consists of learning the basics of the unique Biorock technology, how they are so effective to restore Gilis reefs and how to maintain, clean, repair and to transplant broken fragments of coral onto it.




  • PADI Advanced open water (or equivalent)
  • Competent buoyancy skills
  • Minimum 20 dives
  • Whilst a marine scientific background is not necessary, a passion for ocean conservation and preservation is encouraged!


  • 15th-27th May 2023  **FULL**
  • 3rd-15th July 2023  ** FULL**
  • 2nd – 14th October 2023
  • 6th-18th November 2023

We’ll be releasing 2024 dates, in September, please check back with us!

Upcoming Course Dates
• 15th-27th May 2023
• 3rd-15th July 2023
• 2nd-14th October 2023
• 6th-18th November 2023

I want to do this!