The National Aquarium, which is set to empty the tanks at its D.C. location after it closes in September, said Monday that it is engaged in negotiations with the federal government that could someday lead to a Constitution Avenue homecoming for its menagerie of sea creatures.

"We are continuing to have ongoing conversations with them," said Tamika Langley Tremaglio, chairwoman of the D.C. aquarium's board. "They've worked very well with us, and we'd love to continue our relationship there, and we're trying to find ways that this will make sense going forward."

The General Services Administration said it has been working for about six years to keep the aquarium inside the U.S. Department of Commerce's headquarters, its home since the 1930s.

"We have worked closely with the National Aquarium to use this as an opportunity to create a more modern facility for them within the same building that faces the National Mall," the GSA said in a statement. "We are committed to continuing to work with the National Aquarium to place them in their new space as soon as possible."

The government also said that it has received from the aquarium "the initial payment for the design phase" of an upgraded facility.

The aquarium said Friday that it would shutter its D.C. operations on Sept. 30 as the government prepared for renovations, which the GSA said would involve cutting the aquarium's electricity.

The aquarium said its 1,500 animals would be sent elsewhere, but officials said they were "committed to maintaining a presence in the capital."

Although the aquarium has been the subject of critical reviews online -- it has a two-star Yelp rating -- its visitation figures have surged in recent years, climbing by 28 percent since 2007. Last year, aquarium statistics show, nearly 205,000 people visited the D.C. branch.

But the number of visitors still lagged well behind the District's other attractions, and nearly every Smithsonian museum logged more visitors.

The aquarium's Baltimore location has proven more successful, drawing more than 1.3 million visitors last year.