THE CORAL REEF -- At the Museum of Natural History.

The trouble with museums is that often everything is stuffed.The caribou still-life looks as if it could breathe behind the glass, yet it doesn't.

But there's something alive in the Whale Hall at the Museum of Natural History: a coral reef microcosm, which the Smithsonian calls "the first successful effort to relocate a reef in total isolation from the sea."

Walter H. Adey, curator of the department of paleobiology, and his group at the Smithsonian collected the specimens this year from the Bahamas and the eastern Caribbean. They sailed in the good ship Marsys (for Marine Systems Lab) Resolute . ("It was a brand-new drug-runner," said Adey. "It was confiscated. We picked it up last spring.") They installed four large aquaria in the ship's hold and filled them with things like parrot fish, surgeon fish, damsel fish and grunts, stony corals, spider crabs, sea anemones and sea urchins, not to mention the horned feather worm.

Though it's just getting started, 80 to 90 species -- thousands of individuals -- have already set up housekeeping in the Smithsonian's coral reef. Eventually a couple hundred species will occupy it.

It has all the comforts of a tropical home. Waves wash over it, thanks to two large buckets that dump water into the 3,000-gallon tank system. Artificial light changes as "day" turns to "night," when the parrot fish literally tuck themselves in for the night, by secreting a membrane around themselves and sitting inside the sack. And the night feeders -- the urchins and crabs -- come out to roam the reef.

There's a lagoon, too, which is really another small tank connected by a flow-through passage. It's patrolled by two baby barracuda, which eventually will be big enough to scare off the other fish and keep them from overgrazing the algae in the lagoon.

Outside in the glass-enclosed laboratory experiments go on and the public can watch: explanations are posted on a bulletin board. Equipment is labeled so the visitor doesn't confuse the brine shrimp-breeder with the algal turf-scrubber. The scrubber was invented (patent pending) to clean the system organically: It uses algae to eat nutrient waste. Adey hopes the scrubber someday will be applied to pollution control.

In setting up the reef, Adey said, "One of the biggest fights we had here was: 'Take it to the Zoo. This isn't the place for it.'"

But it stayed, and it's not at all like the "little carnivals," which is Adey's word for aquaria that "show jumping porpoises and mermaids feeding porpoises."

"We aren't trying to keep some pretty organisms to show people," he said, though the reef is, in fact, very pretty. "We are into something completely different. We are into communities and systems."

With the help of algae as food that grows like a lawn on the reef, the community is starting. Adey says it's still in the colonial state, and the growth rate of the coral is about zero. A pilot reef project in the basement of the Smithsonian took almost three years to establish itself, but this one may need only a few more months.

In the pilot model, coral have approached roughly natural rates of growth. The maximum, he says, would be a centimeter a month, for the staghorn and elkhorn coral, which look like their names. Other species can only manage a millimeter a month.

Now the highest growth rate he's ever heard of for an entire reef in the wild is 15 millimeters a year. The average is four or five millimeters, or about two-tenths of an inch. And only the little animals on the surface of the coral are living; underneath is just an accumulation of coral skeletons.

"Like cities, they build," he said. "Because they build they change their environment, and in many cases they build themselves out of existence."

If all goes well, how long until the Smithsonian's coral reef grows to the surface and does itself in?

Adey leaned back and said, "Oh, about a thousand years."