WASHINGTON - When you talk about the National Aquarium, many people think of the one in Baltimore. And when you say, ''No, the one in D.C.,'' people tend to scrunch up their noses and say, ''Oh, yeah, the one in the basement of the Commerce Department. I was there'' - they pause - ''once.''

Bob Ramin, executive director of the National Aquarium, knows the look and understands it. But if you haven't been to this home to sharks, piranhas, seahorses and alligators in a few years (or especially if you've never been), Ramin thinks now is the time to venture forth.

The 10,000-square-foot aquarium is putting the finishing touches on a five-year, $2 million-plus renovation that has made life for its inhabitants better, with improvements to water and tanks. But visitors have not been left out as the nation's oldest aquarium got a facelift and a new focus.

''This is an extreme makeover,'' Ramin says with a laugh. ''We're still small, so we can't do dolphin shows, but we can focus on national marine sanctuaries.'' To that end, the aquarium has a new theme (''America's Aquatic Treasures'') and new residents, about which Ramin sounds like a proud new papa. ''We have the world's most adorable baby loggerhead turtle . . . some new species of seahorses and some beautiful new eels.''

Gone are the outdated signs, threadbare carpet and dingy walls, replaced with backlit, easy-to-read displays, a larger gift shop, more-diverse critters and more.

Depending, of course, on your perspective, one of the best aspects of the National Aquarium is its size. Sure, it lacks the jaw-dropping quality of its massive cousin to the north, but it also lacks the three-hour time commitment and the $21.95 admission.

Ramin wants people to come and check out the new look and say, ''Wow, this is worthy and cool and educational - and you can see it all in 45 minutes.''

After all, when was the last time you could say that you spent your lunch with sharks - real sharks, we mean, not your co-workers?

National aquarium

* LOCATION: The aquarium is in the basement of the Commerce Department at 14th Street and Constitution Avenue NW, in Washington, D.C.

* WHAT IT WILL COST: $5, $4 seniors and military, $2.50 for ages 2-10; younger than 2 free.

* HOURS: Open daily 9 a.m. to 5 p.m.

* EXTRAS: If you can take a late lunch, you can see the critters eat. Daily animal feedings are at 2 p.m.

* MORE INFO: Call 202-482-2825 or visit www.nationalaquarium.com.