National Geographic Society Newsroom

National Aquarium Unveils World’s Largest Reproduction of Indo-Pacific Coral Reef

This month, the National Aquarium in Baltimore opened a new permanent exhibit, Blacktip Reef. Based on the Indo-Pacific reefs found across a large swath of oceans, the exhibit is the largest of its kind in the world. Ocean Views spoke with the aquarium’s general curator, Jack Cover, about the new exhibit. How did you get...

This month, the National Aquarium in Baltimore opened a new permanent exhibit, Blacktip Reef. Based on the Indo-Pacific reefs found across a large swath of oceans, the exhibit is the largest of its kind in the world.

Ocean Views spoke with the aquarium’s general curator, Jack Cover, about the new exhibit.

How did you get into this exciting line of work?

Jack Cover: I’ve been with the aquarium over 25 years. I’m originally from Baltimore, then travelled around for different jobs, but came back to this area.

For a while I specialized in reptiles and amphibians, which is neat because we do have a sea turtle in the exhibit. But I’ve always had a connection to the Chesapeake Bay and to water in all ecosystems.

What makes Indo-Pacific reefs special?

Indo-Pacific reefs are Old World reefs, they include Australia’s Great Barrier Reef, and reefs off places like Fiji and the Solomon Islands. They are a bit older than Caribbean reefs and have a bit more diversity.

Think of the Great Barrier Reef as basically a mountain ridge near the sea’s surface, and the live coral grows on top of that ridge. Coral is a colonial animal; stony coral is made up of pockets for individual polyps, which deposit limestone as they grow, on top of their ancestors. It may look like a bunch of rocks, but it is a living animal, closely related to jellyfish and sea anemones. If a piece of the reef breaks off, it can repair itself.

The polyps catch zooplankton and are also solar powered, since they have algae that live with them and produce food for them. The coral structure provides lots of shelter and hiding places for lots of other animals.

A coral reef is like a city of the ocean, like New York City, with lots of physical structure and lots of diversity. Small creatures hide in the coral at night, where larger predators can’t get to them. Apex predators hang around.

National Aquarium staff work on faux coral for the Blacktip Reef exhibit. Photo courtesy National Aquarium
National Aquarium staff work on faux coral for the Blacktip Reef exhibit. Photo courtesy National Aquarium

What animals do you have in Blacktip Reef?

We’ll have 20 blacktip reef sharks. It’s an iconic species for shallow water and a beautiful animal, with fins that look like they have been dipped in black ink. They form social groups and hunt in a cooperative manner. We want to get away from this whole Jaws, scary image of a shark.

We also have other species of shark, each with its own niche. We have wobbegong

sharks that are bottom dwellers that blend in with the habitat, and we have zebra sharks. We have rays that will eventually reach a size of six to seven feet (1.8 to 2.1 meters) from wingtip to wingtip.  The reticulated whiptail ray has incredible colors.

We also have schools of unicorn fish, tangs, wrasse, diamond fish, angelfish, oriental sweet lips…some really colorful fishes.

How did you “train” the reef sharks?

We do some training of the sharks before they go into the exhibit, to cue them in that it’s feeding time. It’s kind of like having 20 dogs: you better have bowls in different parts of the room or there will be a feeding frenzy.

So we have four feeding stations, with targets that tell them when it’s time for food. So the low guys on the totem pole all get fed, because there is a hierarchy. Many of them have individual personalities.

The target is a colored hexagonal plate. They learn that when they see the plate come out food is coming, so they should line up. The key to keeping sharks with prey animals is keeping their tummies full. We make it easier for them to get fed than chase small fish.

Does the exhibit have live coral?

There is no live coral in this exhibit. We have it in other exhibits, but it requires a tremendous amount of bright light. We would need the equivalent of the lights at a nearby ballpark. The front of the exhibit would have to have a filter on it, like a sunglass, or it would be too bright. It would take hundreds of years for corals to grow to the major structures that we have. And they are somewhat fragile, if a 500-pound (227-kilogram) sea turtle bumped into it, it would break.

As a conservation organization, we wouldn’t want to harvest live coral from the wild. But what we created functions like real coral in that it provides structure and places to hide. When a predator comes it is like a high school bully walking down the hallway, they give them space.

How was the faux coral recreated?

We wanted to faithfully recreate reef species, so as you go deeper the coral species change. The exhibit is divided into microhabitats, such as a cave, which has more sponges and corals that live in lower light.

So the first thing we did was make a clay scale model of the space. We did 3-D printing of the pipes, to put in all the infrastructure. We had to make sure we had room and checked all the sightlines. Then we took photos of real habitat, to recreate it down to the last detail.

Then we took Styrofoam and carved it into the general shape, with nooks and crannies. Then we laid fiberglass cloth on that, like building a boat, and put different resins on it to give it a rough form. The foam was taken away to make it hollow, so we could run plumbing through it. We then added a texture coat of polyester resin.

All the materials have to be completely inert and harmless to aquatic animals. These structures also have to be strong enough so if the tank was drained it could hold the weight of a sea turtle.

We mixed in different types of sand and painted it. Once we had the basic structure, we made various species of coral: table, brain, staghorn, branching, and so on. We took real coral skeletons and made molds. We then put on a silicon rubber, for what we called the glove mold, because once that hardens it comes off like a glove. We poured in urethane to make the model.

The next part is where it gets a bit complicated. You could paint it red so it matches an image of the real thing, but when you place it six feet down it looks brown, because water blocks different wavelengths of light differently. It blocks red first. So we did color correction so it looks the right color at the right depth. Then we got them oriented so they look as they do in the wild.

The end product looks like you are actually on the Great Barrier Reef.

Aquarium staff match their designs with photos of real coral
Aquarium staff match their designs with photos of real coral. Photo courtesy National Aquarium

How long did it take to make the exhibit?

We did this on a pretty quick timeframe; we started a year and a half ago with the concept.

Where did the animals come from?

Calypso is a female green sea turtle, which is a pan-tropical species. She was found on a beach with netting wrapped around one flipper. It got infected and had to be removed. She’s a poster child for marine debris.

Many of the fish we’ve brought in from different suppliers in Australia. One in Cairns does sustainable collecting on the outskirts of the Great Barrier Reef. The sharks were collected at a small size, and were collected in a way that did not do any damage to wild populations.

They were shipped in a small pool to LA on an airplane and then sent to Baltimore. They went into our quarantine area, where we remove any parasites before they go in the big community tank.

What was the hardest part about making the exhibit?

Trying to stay true to the detail of it and the coordination of all these things. Below the exhibit is the pump room, where you have to duplicate all those water purification things that happen in the ocean. We have ozone that is used to treat drinking water, a drum filter that is used to treat waste material, and devices to mimic tides flushing through. We have to hide all that stuff and make sure there are no dead spots in the exhibit.

We had to make sure nothing will break off and that nothing is toxic. We had 1,003 50-pound (23-kilogram) bags of sand, going down in a line of people, like putting out a fire.

We had to work with the magnification property of water, which makes a coral two to three feet (0.6 to one meter) away look right there.

What does the exhibit look like?

The cool thing about this exhibit is that you’re seeing it from all these different perspectives. You start by walking over a bridge, and looking down at the sharks. They flock like birds. Then you go down to being in a big bubble in the reef, with a very clear acrylic window. You are eye to eye with the whole gamut, from small fish like damselfish all the way to the big ones The turtle may swim below you or above you.

It’s almost like you’re a diver, and your jaw just drops open. This is a cool place.

Staff fabricate a range of corals to mimic natural diversity
Staff fabricate a range of corals to mimic natural diversity. Photo courtesy National Aquarium

What do you want people to take away from the exhibit?

Number one is that it’s a beautiful, very special place. The aquarium’s mission is to inspire conservation of aquatic treasures, and Indo-Pacific reefs are a true treasure.

We also want people to understand that things they do will affect the health of the reef, even if they live far away. People will hopefully look at sharks in a different light, and see them as part of a self-sustaining aquatic community.

We’re burning fossil fuels, putting excess carbon into the atmosphere, and that ends up going in the ocean. It creates carbonic acid, so the whole limestone structure will dissolve if the ocean acidifies. We want people to fall in love with that place and start to think about things they can do to start protecting it.

Visitors can drill down on these issues in computer interactions. Each animal has conservation issues; sea turtles get caught in drift nets, sharks are harvested for fin soup. Humans are removing sea turtles and sharks at a rate faster than nature can recreate them.

This Q&A has been edited.


Brian Clark Howard covers the environment for National Geographic. He previously served as an editor for and E/The Environmental Magazine, and has written for Popular Science,,,, Yahoo!, MSN, and elsewhere. He is the co-author of six books, including Geothermal HVACGreen LightingBuild Your Own Small Wind Power System, and Rock Your Ugly Christmas Sweater.

About National Geographic Society

The National Geographic Society is a global nonprofit organization that uses the power of science, exploration, education and storytelling to illuminate and protect the wonder of our world. Since 1888, National Geographic has pushed the boundaries of exploration, investing in bold people and transformative ideas, providing more than 14,000 grants for work across all seven continents, reaching 3 million students each year through education offerings, and engaging audiences around the globe through signature experiences, stories and content. To learn more, visit or follow us on Instagram, Twitter and Facebook.