Forget the sharks. The most dangerous specimens currently on view at Baltimore's National Aquarium are dozens of ugly, splotchy, whitish gobs collecting on the outside surfaces of the central tanks.
The substance is called leachate, a chemical discharge indicating that the two huge concrete tanks, not quite 11 years old, are falling apart. What the leachate means is that the aquarium may soon face the most trying times in its storied history.
In September 1993, the aquarium will close and empty the central tanks. During the shutdown, expected to last for at least nine months and perhaps much longer, the aquarium plans to complete a $10.3 million renovation. Taxpayers are being asked to foot $8.75 million of the bill.
The shutdown comes at an inauspicious time. With February's open ing of a critically acclaimed aquarium in Camden, N.J., Baltimore now faces nearby competition.
It comes just when the National Aquarium can least afford comparisons. Already the beluga whales, proven star attractions, are gone after one died last year in a collision with a dolphin.
Now, because of the coming repair work, the aquarium will also be without its popular shark exhibit and the Atlantic Coral Reef. With fully one-quarter of their visitors coming from Pennsylvania, aquarium officials are acutely aware of the competitive threat during a period of renovation.
"Right now we feel we are the best," said Frank A. Gunther Jr., chairman of the aquarium foundation's board of trustees. "If you lose that reputation as the best, it's very difficult to get it back."
Still, Mr. Gunther said, the shutdown is unavoidable.
"The nature of the beast is a short life span," Mr. Gunther said.
"Sure, nobody is happy to have a ring tank last only 12 years [actually less than 11]. But we were cutting edge when we were built. Naturally, the technology has improved since then."
At least one report suggests, though, that the deterioration was premature, raising the possibility of inadequate work during the original $21.3 million construction project.
Aquarium officials stress that the tanks are not in danger of imminent collapse. Not yet anyway.
"You can walk away and do nothing," said Emer C. Flounders Jr., an engineer hired by the aquarium for the project, "but eventually you'll have to shut it down."
The city of Baltimore, which owns the aquarium building, already has anted up $250,000 for the project.
In November, Baltimore voters will be asked to approve $3.5 million for the aquarium from a city bond issue.
Then, next year, the General Assembly will receive a request for another $5 million from state bonds.
Aquarium officials say the public money is crucial. They are likely to often remind voters that the National Aquarium is the state's biggest tourist attraction, one that is, in the words of director Nicholas Brown, "vitally important to Baltimore."
They will also make clear that if they have to raise all the money privately, the repairs will take much longer, giving the new Camden aquarium greater opportunity to slice into the National Aquarium's attendance.
"If we stumble," Mr. Gunther warned, "it will be very difficult to regain the niche that we have now." During the shutdown, Mr. Gunther said, the aquarium plans to have alternative exhibits, including a laser show.
He said the aquarium is also considering cutting its ticket prices during the shutdown.
As it is, the aquarium says it has delayed the repairs until the last moment.
Although the deterioration of the tanks was discovered in 1988, the aquarium was then busily erecting the $35 million Marine Mammal Pavilion and couldn't consider shutting down the central tanks without another attraction ready.
It also had to virtually rebuild the so-called "deep dive" -- once the home of the dolphins and then the beluga whales and now rays -- which was beginning to leak badly.
Although the aquarium has emphasized the necessity for the structural repairs to the concrete tanks, that work actually represents a small part of the project, only about $1.5 million worth.
The aquarium is taking advantage of the emptied tanks to attend many other matters as well.
About $270,000 will go to repair the floor one story below. That fTC floor, above a reservoir tank, supports the life-support apparatus of the central tanks. It was never treated with protective coating and, supported now by makeshift wooden beams, is near collapse.
The aquarium will police the huge observation windows of the central tanks. It will restore the frayed mural above them. And it will replace, at a cost of $1 million, the coral reef, which is disintegrating in the salt water.
Hidden from view of visitors, the aquarium will also fully upgrade the life-support system for the central tanks, creating three separate systems, one for each tank and a third to support the adjoining deep dive. Aquarium officials say the fish in each exhibit can be treated more effectively if they have independent water systems.