The National Aquarium, fileted from the federal budget last year, is still in operation in the Commerce Department building at 14th and E streets NW, and the new curator says things are going swimmingly.

"It's never been better, as far as I'm concerned, and I've been here six years," says Brian Montague, who was hired when a nonprofit corporation took over the 110-year-old landmark last March.

Government funding for the aquarium was dropped when its parent agency, the Interior Department, took a look at its stringent 1982 budget figures, eyed the little-known and little-used aquarium and said, in effect, "No tanks."

The supporters of the watery retreat made waves, and eventually the National Aquarium Society, headed by Midge Baldrige, wife of Commerce Secretary Malcolm Baldrige, was formed to take the little aquarium off the government's hands and put it on a pay-as-you-go basis. That's $1 for adults, 50 cents for kids.

Montague says that more than $40,000 has been raised from private sources to upgrade the facility and more space in the building has been found.

Last week, Montague was busily planning the aquarium's holiday special, a 30-gallon tank with bright red fish swimming around underwater ornaments.