In July 2020, 128 terracotta tiles printed by a robotic arm were installed in the Hoi Ha Wan marine park in Hong Kong. They covered about 40 m². Four years later, nearly nine out of ten transplanted corals were still alive, according to the team that designed them.
This result is real. However, it does not mean that reefs will be “saved soon,” as the first version of this article promised.
So we reviewed the topic project by project, with dates, materials, and published results. And we kept the tough question: what weight do a few hundred square meters hold against the bleaching of corals on an ocean-wide scale?
Which 3D printed reefs have really existed since 2012?
Documented projects remain few and small. The most cited are sandstone blocks printed in the Persian Gulf in 2012, six reefs installed in Monaco in 2017, the MARS modules from Reef Design Lab in the Maldives in 2018, and the terracotta tiles from the University of Hong Kong in 2020, which later became the offering of the startup Archireef.
| Project | Location and installation date | Material | Known results |
|---|---|---|---|
| Blocks by James Gardiner and SOI | Persian Gulf, 2012 | Printed sandstone | No numerical follow-up found |
| Larvotto reefs | Monaco, October 2017 | Dolomite sand and volcanic ash, 6 reefs of 2.5 t | Follow-up 2019-2022 (ECOMERS laboratory): colonization comparable to natural rock |
| MARS, Reef Design Lab | Summer Island, Maldives, August 2018 | Marine concrete and ceramics cast in printed molds | No published numerical results found |
| HKU tiles, then Archireef | Hoi Ha Wan, Hong Kong, July 2020 | Terracotta fired at 1,125 °C, 128 tiles, about 40 m² | 88 to 91% of corals alive after four years (preprint, 2025) |
One detail changes the interpretation.
Not everything is printed directly. In the Maldives, the marine concrete and ceramics of MARS are cast into molds themselves printed in 3D, according to the project presentation by Summer Island hotel in August 2018. The previous version of this article also mentioned steel and installation at 7 meters depth. We found no dated source for these two points, so we removed them. Yet the initial idea holds, since the printer mainly serves to copy the complexity of a natural reef, with its holes and overhangs, where a smooth concrete block offers little grip for larvae or fish.
What do the published results in Hong Kong say?
It is the only project on the list followed in detail over four years. Of 378 coral fragments transplanted to Hoi Ha Wan, 88% were alive at the end of the follow-up according to the body of the study, and 91% alive and well attached according to its summary. The authors also counted seven times more fish than on the nearby unrestored seabed.
These figures must be read with their context.
The study by Vriko Yu, David Baker, and their colleagues was posted online on bioRxiv in June 2025. It had no peer-reviewed published version when we consulted it. Vriko Yu and David Baker also co-founded Archireef in September 2020, the company selling these tiles. Nothing unusual there; applied research often works this way. But a cautious reader notes the link, as well as that in April 2023 the same founder announced 98% survival at the Eco-Business site, a figure more flattering than that of the study.
Not all corals grew at the same rate. Branching corals of the genus Acropora grew about 0.35 cm per month, versus 0.14 cm for Platygyra, a slow-growing brain coral (if you want to review these shape differences, our complete coral guide details them). Another contribution comes from environmental DNA. By filtering water, researchers detected 13.3% more eukaryotic genetic variants than on a nearby natural coral community, and 23.5% above the unrestored zone. They themselves acknowledge the limitation of a single sampling, done two years after installation.
Monaco and the Maldives: what have we learned after installation?
In Monaco, six reefs printed in dolomite sand were submerged at the end of October 2017 in the Larvotto marine protected area. The follow-up conducted from 2019 to 2022 by the ECOMERS laboratory of Côte d’Azur University concluded colonization comparable to natural rock. In the Maldives, no published numerical results were found for MARS.
The Monaco case deserves attention. These reefs were not installed to regrow tropical corals, as there are none in Larvotto. Their goal was to recreate shelters for fish and invertebrates by mimicking the complexity of a rocky seabed, according to the announcement made by Monaco and its partners in 2017. The follow-up even used a hyperspectral camera, presented by the Prince Albert II Foundation as a first in the Mediterranean. Thus, the result is encouraging for an artificial habitat, without saying anything about the fate of coral reefs.
In the Maldives, the silence is more troubling.
Summer Island and Reef Design Lab announced in August 2018 that they wanted to study how corals acclimate to marine concrete and ceramics, then share their observations. Eight years later, no numerical trace has been found. The follow-up may exist without being published, impossible to decide here.
Why won’t 3D printing save reefs alone?
Because the scale does not keep up and the cause of decline remains intact. Archireef announced in April 2023 a little over 300 m² installed between Hong Kong and Abu Dhabi. A systematic review published in 2020 in PLOS ONE finds a median restored surface of 100 m² per project, with an average coral survival of 66%.
To give you an idea, 300 m² is barely larger than a tennis court.
The same review notes that 60% of projects publish less than 18 months of follow-up, with a median duration of 12 months. That’s short for coral. However, the real obstacle lies elsewhere. Nothing indicates that a well-designed tile protects a transplanted coral from a massive bleaching event, since the support does not change the water temperature around it during a marine heatwave. As early as 2018, the Mongabay site reminded that 3D printing does not solve acidification or bleaching. It mainly serves research on restoration.
In short, we see it as a local tool, useful where the seabed has been destroyed and where the water remains livable for corals. Approaches on more heat-tolerant corals, like those that better resist warming in the Red Sea, advance in parallel. None replace emission reductions.
How to read a 3D printed reef announcement?
Look for four things before believing it: installation date, actual surface area, follow-up duration, and type of publication. A company press release, a news article, and a peer-reviewed study are not equivalent. If one of the four is missing, keep the announcement as a lead.
Take the survival figure. In Hong Kong, it goes from 98% in the press in 2023 to 88 or 91% in the 2025 study, depending on whether counting living corals or living and attached ones. The gap remains modest. Yet it shows that an announced rate depends on how counting is done and when. And look at what serves as comparison, because a restored site compared to a bare rubble bottom will always start ahead.
For a diver, the useful share remains modest.
On a restored site, do not touch structures or marine life, keep your fins off the bottom, and choose a sunscreen less harmful to corals. These actions will not save a reef either. They just avoid damaging underwater, in seconds, what a team took four years to monitor.
FAQ
Is 3D printed coral real coral?
No. The printer makes a support in terracotta, concrete, or dolomite sand. Living corals are then attached as fragments, or organisms settle there over time.
Can 3D printing save coral reefs?
Not by itself. Followed projects cover from a few dozen to a few hundred square meters, and a new support does not lower the water temperature. It helps locally restore destroyed seabeds and test habitat forms.
What results have been obtained in Hong Kong?
Of 378 fragments followed for four years at Hoi Ha Wan, 88 to 91% were alive depending on counting method. The study, posted online in June 2025 on bioRxiv, is a preprint partly signed by Archireef co-founders.
Can you dive on a 3D printed reef?
The cited sites are in marine protected areas, such as Hoi Ha Wan or Larvotto, where access rules depend on the manager. Check with them or a local club before planning a dive, and do not touch the structures.
Sources
- Coral restoration – A systematic review of current methods, successes, failures and future directions (Boström-Einarsson et al., PLOS ONE, 2020)
- Assessing the Effectiveness of 3D-Printed Ceramic Structures for Coral Restoration: Growth, Survivorship, and Biodiversity Using Visual Surveys and eDNA (Yu et al., bioRxiv, preprint, 2025)
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