Dawn – or sunset – for the age of aquariums?

When it comes to fierce sharks, charismatic penguins, rainbow-colored fish, and fire-red coral, millions of aquarium visitors each year aren't the only ones who are dazzled – so are civic leaders coast to coast.

They see not just a paradise in aquamarine, but also a sea of financial green.

In the 1990s, aquariums were being built nearly as fast as new Walgreens as cities tried to generate development of downtown areas and waterfronts. On average, one aquarium has opened each year for the past 12 years, a 50 percent increase over the 25 "accredited" aquariums that existed prior to 1990.

"A lot of cities have looked at aquariums as an economic panacea," says Debra Kerr Fassnacht, executive vice president of the venerable Shedd Aquarium in Chicago.

But for every success story, there are other aquariums that have struggled to keep their turnstiles revolving. With more and more cities erecting tanks of fish, the novelty of aquariums may be wearing off.

Earlier this month, Denver's Ocean Journey came within a day of closing its door. Choked by a tide of red ink – nearly $63 million in debt – the aquarium staved off oblivion with a last-minute Chapter 11 bankruptcy filing that will ensure its continued operation for at least a few months.

Other cities besides Denver have found the lure of the deep led them deep into debt. Government bailouts rescued Aquarium of the Pacific in Long Beach, Calif. and the Florida Aquarium in Tampa. After a decade of operation, the New Jersey State Aquarium in Camden continues to attract hundreds of thousands fewer visitors per year than was originally projected. And after large opening crowds, the South Carolina Aquarium in Charleston has seen a larger-than-expected drop-off. Smaller aquariums from Alaska to Minnesota have also had financial problems.

But the experience in Denver and elsewhere may not slow the feeding frenzy – there are over two dozen new aquariums in various stages of development, according to Jane Ballentine, a spokeswoman for the American Zoo and Aquarium Association.

The surge in aquarium building is generally attributed to the success of two titans of the deep: the National Aquarium in Baltimore, and The Monterey Bay Aquarium in California. Both opened in the early 1980s, acted as economic redevelopment anchors, and continue to shine as bright as glo-fish with each drawing an average of 1.7 million visitors a year.

But now, some experts say there are too many aquariums. Whether or not aquariums have reached the saturation point may well be tested in the next few years in the Southeast. The Tennessee Aquarium in Chattanooga has been highly successful, drawing close to 1 million visitors annually for a decade. It had already faced with competition from four aquariums in the Carolinas before the Charleston facility and a Ripley's for-profit aquarium – only 120 miles away in Gatlinburg, Tenn. – opened in 2000.

But the ultimate test is yet to come. Last fall a cofounder of Home Depot pledged up to $200 million to build an Aquarium in Atlanta by 2005.

The key factor for an aquarium's success, however, may lie in the business model.

Healthy aquariums in Monterey, Baltimore, and Chattanooga were fully paid for when built so that ticket revenue only has to cover operational expenses.

In Denver, Long Beach, and Tampa, the aquariums were saddled with heavy debt service on top of operational costs.

Still, it's not all about finances, there are the fish, too. "One of the main ingredients for success is product," says Jackson Andrews, director of operations and husbandry at the Tennessee Aquarium. "You have to have product."

Indeed, aquariums are faced with heightened competition for leisure dollars as ever more exotic theme-park rides raise Americans' entertainment expectations.

In response, aquariums are introducing splashy new exhibits. The Tennessee Aquarium will open a sea horse exhibit on May 1. Shedd will debut a new wing next year with a Philippines coral reef that will feature sharks. The Baltimore aquarium is embarking on a 10-year renovation that will double its capacity.

"We're just opening up the greatest temporary exhibit ever done," says Monterey's Hekkers. "It's an exhibit that combines live jellyfish with art, particularly blown glass. It's like entering another world."