Home &garden | No yard No problem for city-side folk who want fish ponds

When Ann and Glen Gage downsized from their expansive home and garden in Switzerland to a San Francisco townhouse, one of the things they missed most was the koi pond they’d built and tended for years. It was brimming with elegant plants, fish and its own ecosystem.

So they built not one but two new ponds, this time city-style: one for their balcony overlooking San Francisco and the other for their leafy entryway.

A patio container pond photo/creative commons

“If you have limited space or want an interesting water feature … patio or container ponds are an easy option, and the only limits are your creativity,” said Marc Hachadourian, director of the Nolan Greenhouses for Living Collections at the New York Botanical Garden.

The Gages assembled their container ponds using large planters, which they made water-tight by caulking any drainage holes. Then they added gravel and a few larger rocks, and filled the container with water. They added an electric bubbler and filter “to make the fish happy.” Next came a few floating aquatic plants, which they harvested from a pond in the area, and finally a variety of “rescue fish” from a pet store.

“We have a really small space, and Ann said, ‘Wouldn’t it be cool to have a pond here?’ It couldn’t have been easier,” Glen Gage said. “It’s way less work to maintain than a big aquarium — no cleaning the tank or siphoning out the dirty water — and there’s a relaxing Zen quality to the gently bubbling water and swimming fish.”

Maintenance involves only refilling the container to replace water lost to evaporation. Although some people put mosquito-killing tablets in the water, experts say a few small fish are sufficient to take care of insect larvae.

“You can go crazy with really fancy fish, but our local pet store is super nice, and they just let us reach in for feeder fish and choose some with pretty markings that make them look unique. It’s like going to the pound. You feel like you’ve done something really good. They’re basically just goldfish and are pretty hardy,” Gage said.

Although the patio ponds can look and feel like miniature koi ponds, koi experts strongly suggest goldfish as the better choice.

Unlike koi, which grow large and need plenty of oxygen and moving water to thrive, goldfish and some other smaller fish are hardier and better suited to patio ponds.

“Putting a koi in a little container pond would be like trying to raise a German shepherd in a box,” said Don Chandler, chairman of Koi USA, based in Costa Mesa. “The smallest possible koi pond would be a 600- or 800-gallon pond. That’s more than most people are ready for on their patio.”

The International Water Garden Society is a good resource when deciding on varieties of aquatic plants. Hachadourian recommends miniature water lilies like dauben, which has a light blue flower and tolerates shadier conditions. Plants such as water lettuce and water hyacinth float on the surface, control algae and help filter the water. Aquatic grasses, irises and tarrow are also good choices, he said.

When deciding where to put a patio pond, first consider how much weight your floor or terrace can handle. Even the lightest container is heavy when filled with water, which weighs a bit more than 8 pounds per gallon. “It’s not what you’d want on a rickety porch,” Hachadourian said.

Ponds also need a good amount of light and work best outdoors. Indoors, they would work in a greenhouse-type area; otherwise they generally require additional lighting.

Although container ponds work year-round in warmer climates, they are more challenging where winters are harsher. Hachadourian said most container ponds, or at least the fish residing in them, need to be moved to a warmer area in winter.

“A lot of people treat patio ponds a bit like annuals and restart their ponds every spring. They just transfer the fish to an indoor aquarium in winter and drain the container pond. In the spring, fast-growing aquatic plants are installed, the fish are put back in the pond, and you’re all set for the warmer part of the year,” he said.