After seeing “Finding Nemo,” the story of a young clown fish and his anxious dad, children may leave the movie theater wanting a Nemo of their own.

But before you zip over to the pet store, be warned: Setting up a saltwater home for a clown fish requires a lot more work than simply filling up a tank and tossing in fish. And it’s not cheap: An initial saltwater system, including tank, filtration system, heater and other basics, could cost $350 or more.

There are PH, nitrate, salinity and temperature concerns. There’s the need for regular water changes. There’s knowing how many fish you can put in a tank and which fish get along.

“You have to maintain a chemical balance in the water,” said Douglas Lockett, an aquarist, or aquarium hobbyist. “It’s like its own little environment.”

Lockett has been an aquarist for about 12 years. He began with freshwater aquariums, but now has only saltwater tanks. Though some say setting up and maintaining a saltwater tank is no tougher than freshwater, Lockett disagrees.

“The saltwater aquarium certainly takes more care,” Lockett said. He advises families to start with freshwater when setting up their first aquarium.

Whether freshwater or saltwater, the responsibility for maintaining the tank should not fall solely on a young child, cautions Ed Martinez, an employee of Exotic Tropicals in Colorado Springs, Colo.

“It’s definitely going to be a family thing,” Martinez said.

Though kids often are short on patience, they’ll need it when it comes to getting a clown fish. That’s because it takes time for the proper environment to take hold in a tank. Martinez advises waiting at least 10 days before adding fish; Rick Hennis, manager of Neptune’s Realm in Colorado Springs, recommends letting the tank circulate for a month.

Hennis suggests starting with a 55-gallon tank. Smaller tanks are cheaper, but it’s trickier to maintain water quality in them.

Once the tank is ready, start out slow — “one or two fish,” Martinez said. The good news is clown fish are relatively hardy. Their cost — about $15 and up — is a drop in the bucket compared to the aquarium setup. And they’re not picky eaters.

“They’ll eat a range of foods, from flake to frozen to live,” Martinez said.

A last warning: Don’t overfeed. Three times a week is sufficient for a clown fish.

“A lot of people have this misconception about feeding three times a day or every day,” Hennis said. “You’ll never have a successful tank if you feed that much.”