New York City has always been a sometimes hectic, stressful place to live and work, and now - perhaps more than ever - New Yorkers can use all the tranquility they can get. Short-term fixes like day spas and weekends at the shore can help, but for a more lasting remedy for the stress and clamor of day-to-day life in a white-knuckled city, maybe you should consider"¦fish.

Yes, fish. Not as in spring rolls and sashimi at Tao, but as in aquariums full of sparkly, darting aquatic critters. Whether in your own home or in your building's common areas, a softly bubbling aquarium can satisfy you and your fellow residents' need for soothing, life-affirming design elements in our tightly wound times. Maybe it's the exotic touch of nature that comes with aquariums, or maybe it's just that everyone likes to watch pretty fishies swimming in hypnotic swirls; whatever the explanation, a luminous tank full of living jewels is fast becoming the hallmark of well-appointed spaces across New York, and residential buildings are jumping in as well.

As far as lobbies go, few things can match a shimmering slice of marine life for making an impression. Want to create an automatic aura of calm? Voila. Want to connote opulence and status without being ostentatious? Done. An aquarium can lend an otherworldly feel to even the most banal surroundings. For a lobby that lacks character, you couldn't pick a better makeover idea; for one that already has some style, a tank might be the crowning touch. But whatever your space is like now, an aquarium is a great investment sure to make residents, guests and potential buyers swoon the moment they walk through the door.

Best of all, an aquarium is an easy and inexpensive way to upgrade your building. Ready to take the plunge? Just follow these simple guidelines, and you'll be well on your way to underwater bliss.

Before you start planning, the first question to consider is whether your lobby or common area can accommodate an aquarium. According to Joe Caparatta of New York Aquarium Service, Inc.,a company that installs and maintains high-end aquariums, the first issue is the load-bearing capacity of your floors. "Water is heavy stuff - about 8.2 pounds per gallon, so you have to make sure your floors can take it," he advises. You may want to consult an engineer if you're getting a large tank. Next, consider light requirements. Too much sunlight will cause algae blooms, says Caparatta, so you need a shady location where you can control the amount of light that gets in. And lastly, fish are highly vulnerable to rapid fluctuations in temperature, so you'll want to pick a stable spot away from doorways and other drafts.

Once you've established that your space is suitable, you must decide - if the aquarium is to be located in a common space, like a lobby or sitting area - who'll be in charge of overseeing day-to-day maintenance. Bear in mind that an aquarium is full of living organisms that will need regular attention after the heavy work of installation is done. Your board will need to determine who will be the liaison with your maintenance service, as well as who will be responsible for feeding and checking up on the fish on a daily basis. Whether you see your fish as pets or as decorations, they won't do well as either one if they are not well cared for. Overfeeding fish is the surest way to kill them (it pollutes the water), so it's crucial to have a strict feeding schedule. Caparatta recommends picking one person to handle feeding to avoid slip-ups. It's also imperative to remove any sick or dead fish immediately to avoid contaminating the whole tank, so someone has to be paying attention in between visits from your service.

The next step is deciding on a budget. According to Eric Clemens of West Coast Aquarium Industries in San Diego - a company that does a lot of large custom projects - there are basically three different types of aquariums: freshwater, saltwater and reef, each with a different price range. (The estimates below are based on a 300-gallon custom tank - which would be roughly 7'x 2'x 3' just to give you an idea of size.) The least expensive kind is a freshwater tank because freshwater fish are easiest to care for. "A 300-gallon freshwater tank would average about $6,500 for installation, $500 for the fish, and an additional $150 per month in maintenance," says Clemens. Next are saltwater tanks. Saltwater fish cost more because the fish themselves are generally more expensive, and maintenance is more intensive. "Saltwater fish can't handle changes in their environment as well because their natural habitat - the ocean - is so stable. So a saltwater tank is basically a life support system - it's a very controlled environment, and it needs a lot more attention," Caparatta explains. The same 300-gallon tank would cost about $8,000, plus $2,000 for live stock, and about $225 per month for maintenance, says Clemens. And finally, there's the ultimate aquarium-aficionado's choice - the coral reef tank. Reef tanks are a recent innovation, and the most expensive choice because you're attempting to recreate a fragile and complex ecosystem in an artificial environment. "Reef tanks are the most spectacular. That's what everyone really wants," says Clemens. Just beware of sticker-shock. A 300-gallon reef tank will cost an average of $15,000 up front, and about $325 per month for maintenance. It can also guzzle a lot of electricity. "You need to run a chiller for a reef tank, and that can get pricey. I had a 75-gallon reef tank that was running up about $100 per month in electricity," Clemens warns.

There's also a tremendous range in the tank design itself - which can impact the final price tag quite a bit. It pays to consider getting a standard tank from the dealer, as custom tanks can cost up to five times more, according to Caparatta. However, if you really want to pull out all the stops, you can have just about anything you can dream up. "We have a thermoforming oven, so we can make a tank in just about any shape," says Clemens. "You can get a freestanding tank or one that's built in to some kind of cabinetry. The cabinetry generally costs about an extra $2,000-$4,000." Then there's the equipment. Caparatta advises investing in top-of-the-line filtration equipment like a Marineland bio-wheel, and getting the largest tank you can afford. "The bigger the tank, the more stable the environment," says Caparatta. The number-one fish killer is ammonia poisoning, which is basically polluted water. So, in a nutshell, invest in a good set-up and you'll be rewarded with happy, healthy fish that cost you less in the long run.

After deciding what sort of aquarium environment you want and where it will reside, the most important decision you'll make is choosing a reputable supplier and service provider. Even after the initial installation is done, there's a lot to know, and you probably don't want to have to learn it all yourself. Caparatta recommends picking one company that supplies stock and offers maintenance. It's your best protection against getting sickly stock, or picking fish that won't work well together. "Pick one company that does everything and build a relationship with them," suggests Caparatta. "Sometimes fish just die, so it's hard to guarantee them. But there's a lot you can do to take preventive measures. Most fish are in pretty bad shape by the time they've traveled from wherever they were harvested or caught to the store. They're stressed; they're malnourished; they're very susceptible to problems. I quarantine all my fish and nurse them back to health before I introduce them to anyone's tank." Buying from a random pet store could put your entire tank in jeopardy. That said, Caparatta advises that if you just can't resist picking out a specimen yourself, check the tank for any dead or obviously ailing fish, and make sure your chosen fish is eating, which is generally a good sign.

Some other safeguards in choosing a service: Ask for references from clients who've been using the service for several years, says Caparatta. Request a free estimate, and make sure it includes name-brand equipment. Find out if you're guaranteed against leaks, and if your installer and tank-maintenance provider has insurance, just in case Murphy's Law kicks in. You might also try to sniff out some science credentials. This is tricky because - unlike veterinarians - aquarium specialists and fish-tenders are not bound by any particular license requirements. "Some pet store guys know everything just from experience," says Caparatta, but a degree in marine biology or a related field couldn't hurt. If you want to educate yourself, there are plenty of resources available. You might want to start with The Marine Aquarium Handbook: Beginner to Breeder by Martin A. Moe, or fire up the computer and go to www.microbelist.com for free advice from Caparatta himself.

Humans have always been fascinated by the mystery and grace of the underwater world. That's why aquariums never go out of style. But as design elements, aquariums are having "a moment," as they say. Rainbow-colored fish flashing through crystal-clear water, scattering clouds of bubbles in their wake may just be the tonic to soothe the harried New Yorker's nerves after a busy day.