The innovative way the Georgia Aquarium manages millions of gallons of tank water

The largest aquarium in the U.S. processes more water in a day than the city of Boston. Here’s what it takes.

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The innovative way the Georgia Aquarium manages millions of gallons of tank water
The Tropical Diver tank

Photograph by Wedig + Laxton

It’s 9 a.m at the Georgia Aquarium and the first visitors of the day are just trickling in, but behind the scenes, staff is already buzzing. So are the sea lions. “Sounds like Jurassic Park, doesn’t it?” says John Masson, Georgia Aquarium’s Director of Life Support Systems, nodding towards the cacophony of hoarse barking coming from across the hall. “The sea lions are definitely some of our noisier animals.”

Behind Masson in the life support systems control room, a wall of video monitors displays the many animals (and plants) who call the Georgia Aquarium home: with around 500 species living in 60 different habitats, it’s the biggest aquarium in the United States and the fourth largest in the world. Keeping the aquarium’s creatures healthy and happy is Masson’s primary job responsibility, along with hundreds of other animal care specialists, from veterinarians to microbiologists. And because all those creatures are aquatic, whether partially or completely, a big part of Masson’s job involves water—a lot of water.

“We process more water in a day than the city of Boston,” says Masson. “Twelve million gallons across the whole aquarium.”

The innovative way the Georgia Aquarium manages millions of gallons of tank water
The Georgia Aquarium has over eighty miles of pipes that ferry water in and out of dozens of tanks. Masson’s team is often visited by sea lions, penguins, and even the occasional alligator out for a stroll with their animals handlers. “Sea lions are surprisingly agile,” Masson says.

Photograph by Rachel Garbus

The innovative way the Georgia Aquarium manages millions of gallons of tank water
The view from above the Tropical Diver exhibit, where artificial waves crash overhead using mechanical buckets. The waves aren’t really necessary for the habitat—”that’s more for dramatic effect,” notes Masson.

Photograph by Rachel Garbus

Visitors to the aquarium enjoy dazzling views of underwater worlds, where giant whale sharks swim overhead and schools of blue tang surgeonfish zip past. On the other side of those underwater worlds, the talented staff at Georgia Aquarium work around the clock to ensure they’re the perfect habitats for the marine creatures who swim, waddle, and splash in them.

Georgia Aquarium is unique not just for its size, but for its location. “Most aquariums are located on the coast, so they can discharge their water into the ocean and get fresh replacement water back,” explains Masson. Georgia Aquarium is landlocked, so there isn’t a ready source of new saltwater, or a place to discharge dirty water. “We can’t exactly dump six million gallons of saltwater into the Chattahoochee River every day and be well thought of in Atlanta,” he jokes.

Instead, Georgia Aquarium operates on what’s called a closed loop: it recycles 98 percent of its water using a complex process of retrieval, cleaning, waste removal, and recalibration. A small amount of water is lost to waste disposal, as well as splashing during dolphin and sea lion shows. “Sea lions are a lot like rowdy dogs,” notes Masson. “It’s very difficult to convince them not to waste water.”

To keep the tanks fresh and clean, water is continuously filtered in and out. Ocean Voyager—the enormous exhibit wrapped over a clear tunnel where visitors can see whale sharks, giant manta rays, and dozens of other animals—replaces all of it 6.3 million gallons in an hour. Fresh seawater is pumped in, while old water is sucked through a series of pipes below the aquarium and transferred to a waste recovery system. A machine called a protein skimmer squeezes out the waste particles, like fish poop and bits of leftover food, which emerge as a dirty foam that goes into the sewer system. You might see the same kind of foam in the ocean, notes Masson, as proteins break down in their natural environment. (“Don’t use it to make a beard on your face,” he cautions.)

The innovative way the Georgia Aquarium manages millions of gallons of tank water
A model of Georgia Aquarium’s closed-loop system for use in school tours.

Photograph by Rachel Garbus

The innovative way the Georgia Aquarium manages millions of gallons of tank water
The protein skimmer sucks waste particles out of old tank water. Waste goes into the sewage system, while the water goes on to be cleaned for reuse.

Photograph by Rachel Garbus

The clean water is then “polished:” staff treats the water with ozone and sends it down the pipes to be filtered back into tanks, which are temperature controlled to mimic the natural habitat of each animal. “Our puffins and spider crabs like the cold, so those habitats are set to 52 degrees,” says Masson. “While the South American discus fish like it warmer, around 82 degrees.”

Meanwhile, in the laboratory, a team of environmental scientists takes daily samples to ensure the water is clean and clear of harmful bacteria or other pathogens. “We want the water to be as close as possible to natural sea water,” explains Susan Walsh, senior manager of environment health. Small bottles are laid out on a counter, with color-coded labels identifying the tank from which the sample was collected, and a volunteer uses a pH probe to test them for salinity and alkalinity. Across the lab, environmental analyst Savanna Evans measures the bacteria levels to ensure they’re safe for marine mammals: the U.S. Department of Agriculture allows aquariums and zoos to keep marine mammals but can remove them at any time if health standards aren’t met. Her team also measures air and light quality, to mimic the natural environment of each creature. “Sea turtles need something different than corals,” Walsh says. “We have to make sure we give each one what it needs.”

The innovative way the Georgia Aquarium manages millions of gallons of tank water
A volunteer uses a pH probe to sample water quality from every habitat.

Photograph by Rachel Garbus

Georgia Aquarium’s closed loop water system is unusual for aquariums, but it may provide a template for others in the future. Environmental regulators have begun limiting the amount of water aquariums can discharge, so new facilities will look to processes like Georgia Aquarium’s to reuse more water. Masson and his team have developed some innovative water-conservation methods they hope to share with more aquariums, including a way to break down hard-to-remove nitrates using natural bacteria and sulfur. And the aquarium is working with Georgia Tech researchers to design other sustainable practices for its water and waste systems. “I’ve been here 18 years,” says Masson. “And I’m always learning something new.”

 A version of this article appears in our April 2024 issue.

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