(FORTUNE Magazine) – THE LATEST MUST-HAVE hedge fund accessory weighs a ton (literally), contains up to ten living creatures, and costs $600 a month--just for upkeep. Aquariums, which were popular in the 1970s, are back. But forget the fish tanks in your dentist's office--these "installations," as they're called, take six months to complete and cost as much as $600,000. The tanks feature specialized glass for better viewing, custom-made furniture crafted to accentuate the colors of the fish, live coral, and rare creatures like angelfish from New Caledonia, which sell for $3,000 each. Angelfish "grunt and have very distinct personalities," says Justin Muir, co-owner and principal designer of New York--based City Aquarium. "They're more like pets."

Aqua-entrepreneur Muir has made a specialty of catering to the hedge fund crowd, who he says continually try to outdo one another. A native of the Massachusetts coastal town of Cohasset, Muir was a licensed lobsterman at age 8, studied marine biology in Hawaii, and previously raised eels in South Carolina. City Aquarium, which he founded in 1999, now has a client roster that includes sultans, supermodels, Russian heiresses, Broadway producers, and an increasing number of hedge funds like SAC Capital Advisors and Sandell Asset Management (both declined to comment on their expensive toys). "Aquariums are status symbols," says Muir, who has also designed aquariums for hedge fund managers' homes. "These guys say, 'Okay, if we are going to do [an aquarium], it has to be hot.' " So what's the hottest thing right now in hedgie tanks? Sharks, natch. The price: around $2,000 each.