Tanks for the anemones: Reef builders pour their all into a new home for the fish

March 29, 1995|By Holly Selby | Holly Selby,Sun Staff Writer

A new colorful, watery world of sand, coral and 43 kinds of fishes has been created at the National Aquarium. Inch by inch, a team of curators, biologists and designers built a coral reef from concrete, polyurethane and fiberglass. Drop by drop, they filled its tank with 335,000 gallons of salt water. And sea creature by sea creature, they made it come alive.

Now French angelfish and grunts, trigger fish and tripletails, jacks and jolthead porgies, lookdowns and spiny lobsters are settling into a new home.

Though the aquarium today is offering a sneak preview to the national press, the official opening of the Atlantic coral reef exhibit is on April 7. It will celebrate the culmination of nearly $14 million in renovations to the aquarium's 220,000-gallon shark tank and the 335,000-gallon coral reef tank. There will be festivities including music and a children's parade throughout that weekend.

The renovations, which began in the fall of 1993, were needed because the steel and concrete structures of the original tanks had been corroded by salt water and were beginning to crack. Aquarium officials seized the chance to build a better reef.

Though real coral reefs resemble colorful, underwater castles, they are actually living colonies of thousands of anemone-like animals known as polyps.

These tiny creatures use their minuscule mouths to get the nutrients they need from the water. The waste they excrete builds up around their soft bodies to form a hard, protective wall of limestone. With skeletons of dead polyps forming the base, and young animals growing on top, the reefs grow at a rate of a few millimeters a year.

Scientists estimate that some reefs may be 30 million years old. And many are being endangered by pollution, overfishing and human development.

Partially because of this, aquarium officials wanted to replicate the reefs as precisely as possible. "The public can get a better sense of what reefs are like and it may instill in them a sense of stewardship for the environment," said Bruce Hecker, curator of fishes.

'What do the fishes want?'

They also wanted to create a comfortable home for the fish. "If their habitat is more natural it will encourage more natural behaviors like hovering near a hidey hole or hanging out under a rock or breeding."

In the old coral reef exhibit, the curators successfully bred sergeant majors -- small, yellow-and-blue fish. Now they hope other species in the exhibit, perhaps trigger fish and grunts, will also reproduce.

Before beginning to design the new reef, "We asked ourselves, 'What is our educational message? What is our conservational message? And what do we want to show the public?' " said Mr. Hecker. "Then we asked, 'What do the fishes want?' "

The reef itself was built in California, a collaborative effort by the aquarium and two companies, the David Manwarren Corp. of Ontario, Calif., and Exhibits Technology of Littleton, Colo.

The aquarium staff first built a small, 50-inch clay model, which was re-created in California as a life-size steel, concrete and foam construction.

Many months, models and molds later, the final product -- large, concrete-reinforced, polypropylene panels -- was ready to be shipped back to Baltimore. All were numbered so that they could be assembled like a puzzle to form the 14,000-square-foot reproduction reef. And all were lowered by crane into the aquarium through a hole in the roof.

Hard or stony corals -- such as brain, staghorn or leaf corals -- were formed by using silicone molds, which were filled with colored urethane. The urethane was allowed to harden in the molds until it formed beautiful, lifelike pieces of "coral."

The soft corals, including sponges and sea fans, had to be individually sculpted by the aquarium staff.

No metal this time

No metals -- part of the problems in the original tanks -- were used. Instead, the coral reef is held together by fiberglass, epoxy and nylon bolts, said Mark Donovan, senior director of designs and exhibits.

The end result is a replica of a reef covered with corals in mustard, red, pink, purple, blue, gold, rust and parrot green. Some stand stiffly like turrets on top of the rocks. Others, replicas of purple fan and yellow whip corals, are made of flexible urethane and filled with tiny "microbubbles" that make them buoyant. When a big fish bumps into them, they bend.

Rock and coral overhangs carved into the exhibit provide places for schools of grunts to congregate. And the small, reddish snouts of nocturnal squirrel fish peek out from nooks and crannies that now form their hidey holes.

While the reef was being created, the tanks needed to be dry. The shark tank was closed in November 1993 and reopened a year later. The coral reef tank was closed in the fall of 1994 and reopened a few weeks ago. While their tanks were being renovated, some sharks were released and a few were loaned to the Maritime Center at Norwalk, Conn. Most of the sharks and fish were kept in warehouses in Fells Point.

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