After six months of record crowds and a flurry of concern for their overworked fish, officials of the new National Aquarium in Baltimore announced yesterday that they will close the $21.6-million facility for 10 days next month to perform a "face lift, uplift and overhaul" in anticipation of the spring tourist crush.

"We're victims of our own success," said acting director William S. Flynn, who announced that the aquarium will close from March 8 to 18. "We have to clean carpets, and repaint hundreds of yards of railings, and only because we've received far more visitors than we expected."

The ultramodern facility has received 800,000 visitors since its August opening, the number projected for the entire first year, and quickly has become a trendy setting for parties and fund-raisers.

The aquarium's popularity brought a rash of problems, however, as the stress of crowds throughout the day and evening wore down the carpets, increased security needs and fatigued the fish and staff. As a result, officials decided to decrease the number of people allowed inside at one time to 800--down from about 1,200--and to restrict social functions to two each week, "instead of the five or six a week we were getting," said Flynn. The fish are feeling much better, he said.

In addition to the minor repair work, Flynn said that a pedestrian railing near the shark tank will be rebuilt, the rain forest cleaned up, and a leak in the dolphin tank repaired. Flynn said that officials decided that closing the facility for 10 days would be less of a burden on the public than performing the repairs one at a time, which would take months. He estimated that the facility would lose about $50,000 in revenues during the 10-day period.

The March closing date was chosen because "we had only one party scheduled ," Flynn said, "and with the weather, we predicted it would be slow."

Marketing director Kathy Cloyd said the repairs would cost the aquarium between $15,000 and $25,000. The city and the original contractors will assume the rest of the costs, she said.