ELGIN, Ill. – It all started with a little water fountain on the patio.

“We thought it would be cool to have a pond,” said Steve Ciaccio.

Now Ciaccio and his wife, Debi, have their own version of paradise in their backyard on Elgin’s east side, replete with two waterfalls and two streams in which 17 colorful koi swim about. To assist with their hobby, the two are among the 500 families who belong to the Midwest Pond and Koi Society.

“They’re down-to-earth people, and we’ve learned a lot from them,” said Ciaccio.

Ciaccio sees his setup as a sort of outdoor aquarium. It’s also an example of an increasingly popular outdoor activity.

“Water gardening and koi-keeping remain the fastest-growing hobbies in the Midwest and probably the U.S.,” said MPKS club president Dr. Robert Passovoy of River Forest. “New clubs are forming every year, and people are being attracted to the hobby by home builders who are including water features as value-added add-ons in their new construction.”

“I learned recently that something like 25 percent of homeowners have some form of koi pond or water garden,” said Mike Robinson of Keystone Hatcheries in Richmond. “Even though that’s a huge number, there is still a lot of room for growth. In Europe, the number is closer to 75 percent.”

As for the costs associated with the hobby, people who raise koi for show can spend thousands of dollars on a single fish, especially in Japan, where koi originated. But for an enthusiast, “koi-keeping is more expensive than solitaire and less expensive than stamp collecting, for given levels of fanaticism,” said Passovoy, whose club has annual dues of $25.

He said a water gardener can construct his own small to medium-sized pond with materials easily and cheaply available at Home Depot for around $1,500.

“Larger ponds with more elaborate filtration systems and fancier landscaping will cost considerably more. Goldfish can be had at any pet store for a couple bucks apiece,” Passovoy added. “Koi healthy enough to survive can be had from reputable dealers for as little as $10 if your timing is right. The MPKS has two koi and goldfish auctions every summer, and good quality goldfish and koi are available at our two trade shows in May and August.”

Passovoy explained that there are about 20 types of koi, characterized by color and skin/scale patterns, with a number of subcategories.

According to Passovoy, they are all carp, inbred and interbred from a red carp found in a farmer’s rice paddy in Niigata, Japan, centuries ago.

Since carp are scavengers and bottom feeders, they eat most anything. Passovoy said his enjoy grapefruit, while Ciaccio said his grandchildren feed theirs pet shop koi food, watermelon and even Honey Nut Cheerios.

Unfortunately, a koi’s brain is the size of an M&M;, Passovoy said, which means they make easy prey, particularly for clever raccoons and herons.

“I had to restock this spring because an animal got into the pond, dislodged my protective rocks and ate all but one of the koi I had,” said Don Hattendorf of Plato Center.

To protect the fish, ponds should not have shallow shores for raccoons to poach from, and there are heat/motion detection devices that spray water to ward off predators. For the big birds, collectors suggest webbing fishing line along a pond shore.

The hardy koi can survive a Chicago winter. All you need to do is keep the water aerated and a spot warm enough to maintain a hole in the ice. In his ponds, the koi hibernate in small underwater caves and aren’t seen until warmer weather, Ciaccio said.