On Goldfish Pond

By Steven A. Frowine

Compared to koi, goldfish are hardier and easier to care for.

Goldfish have long been revered in Asia, where the Chinese refer to these colorful and graceful fish as "butterflies of the water." Under many dynasties, they were raised in special ceramic pots for the enjoyment of the emperors. Goldfish are still commonly depicted in many forms of Asian art, from jewelry to scrolls to ornamental glass eggs.

Today, many gardeners in North America are incorporating goldfish into water gardens. Whether placed in a small in-ground pond or in an aboveground pool, goldfish are a colorful, low-maintenance, and rewarding addition to any water garden.

Types of Goldfish

There are many different types of goldfish, from those with fan, fringe, or veil tails, to ones with exotic flowing fins or hoodlike head growths. Although all the goldfish types can be displayed in a water garden, some varieties are hardier than others, making them a better choice if you plan to overwinter them outdoors in a cold climate.

The three types that I have found to be the easiest to care for are the Comet, Ryukin, and Shubunkin.

The Comet is the only type of goldfish credited with being developed in the United States. This quick-moving narrow-bodied fish is most commonly orange or white with a red head. It is named for its tail, which is long and trailing like that of a comet. It is extremely hardy. This fish is the kind most often seen in fish bowls.

Ryukins are most popular in Japan and China. These round-bodied fish are usually red-orange or red and white, and display a butterfly-like double tail best viewed when looking down at them as you would in a water garden.

Shubunkins, much admired by British water gardeners, are starting to become better known in North America. Preferred kinds are calico-colored blue, orange, and white. Like the Comet, Shubunkins are hardy, narrow-bodied fish, although their tails are shorter.

Goldfish versus Koi

Although both goldfish and koi are related, they are not the same. A couple of key differences make goldfish a much better choice for a home water garden. Koi grow much larger than goldfish (18 to 24 inches compared with 8 to 10 inches). More importantly from a water gardener's point of view, koi are voracious plant eaters. Goldfish will nibble at some plants but don't do nearly as much damage as koi.

Also, koi are best raised in pools with specially designed filtration systems. Such elaborate (and often expensive) systems are not necessary with goldfish unless you want a large number of them in your pool or water garden. The only piece of equipment necessary for goldfish is an airstone or small water pump to aerate or circulate the water in hot weather. When temperatures exceed 75° F, goldfish can become stressed by the water's low oxygen content.

Another advantage is that fine goldfish are available at garden centers, water gardening specialists, and aquarium stores for a fraction of the price of koi. Quality goldfish cost between $5 and $50, on average, depending on their type and size; koi can cost 10 to 100 times that.

Keeping Goldfish Healthy

Most goldfish are naturally hardy and require only a few conditions to keep them in good health. One of the most common problems arises from adding too many fish to a pool. The result is that fish waste pollutes the water, which becomes the perfect habitat for green algae to form. Green algae grow suspended in the water, turning it murky green and making it difficult to see the fish. Excessive algae can kill fish. If the algae suddenly die or are killed with chemicals, the decaying plants will use more oxygen, and as a consequence, the fish will suffocate.

At a maximum, add only one fish for every 30 gallons of water; fewer are even better. If your pool or pond has no filtration or aeration, reduce the number still further. Also the larger the surface area of the pool or pond, the more oxygen there will be in the water.

The best time to add goldfish to a pool or pond is in early spring after the water temperature has reached 60oF. The water should contain no chlorine or ammonia. Many municipal water companies add chloramine (a combination of these chemicals), which is very toxic to fish. To be safe, you can add a water conditioner such as Amquel, available from aquarium stores, that neutralizes both of these chemicals.

Plants are critical elements in a water garden and are appreciated as much by the fish as by the gardener. They provide protective cover for the fish and absorb nutrients in the water, substantially reducing green algae blooms. Goldfish are compatible with most plants. I've planted cannas, water lettuce, nymphaeas, sedges, and waterlilies in my water gardens. As long as the fish populations aren't too high, you should not experience noticeable plant damage.

Overfeeding is the most common cause of death or decline among goldfish. If your pool is well planted, it is not necessary to feed the fish at all except, perhaps, when you first add them; they will have plenty to eat with the existing populations of algae, mosquito larvae, and other water insects. However, feeding the fish brings them to the surface so you can better enjoy their bright colors.

If you choose to feed your goldfish, use a commercial pellet food such as Hikari or Nippon, giving them only as much as they can consume within 5 minutes. If you give them too much, the extra food pollutes the water and ultimately kills the fish. Replacing 10 percent or so of the water in your pool with neutralized tap water every few weeks is a simple yet effective way to protect against any accumulation of pollutants from fish waste or overfeeding. Goldfish eat very little when the water is cold, as in spring and fall, so take care not to feed them when temperatures in your area dip to 50oF.

Goldfish can be kept outdoors for most of the year. I keep mine in two 4- by 8-foot, 3-foot-deep aboveground pools, which I constructed. These pools, lined with PVC, which lasts for 10 to 20 years, are easy to maintain. Because the pools are raised, you can sit on the edge to observe the fish up close. Keeping your fish in a small pond is another option, though a less appealing one when it comes to protecting them from predators.

The most common goldfish predators are herons, raccoons, and cats. All of these animals will wade into water to stalk the fish. The most effective means of guarding against these predators is to use an aboveground pool with straight, deep sides so they can't wade in. The fish will be able to quickly swim to the bottom to escape any predator able to perch on the edge. Another option is to cover the pool or pond with netting at night.


For many gardeners, overwintering fish creates a great deal of anxiety, but it is really quite straightforward. You can choose one of two methods. One is to leave the fish outdoors if you have an in-ground pool or pond. Goldfish are naturally cold-water fish, and as long as the pool or pond does not freeze solid, the fish will do fine. The main concern is that if ice freezes across the entire surface of the pool, noxious gasses resulting from decomposing leaves and other organic matter in the water will have no way to escape and will be lethal to the fish.

The necessary depth of the unfrozen section varies with the severity of your winters, but for most cold-weather areas (USDA Hardiness Zones 4 through 6), a depth of 3 to 4 feet in part of the pool is usually sufficient. As a safety precaution, you can add a floating cattle water trough heater, which has a built in thermostat, to keep at least a section of the pool from freezing solid.

You can also bring goldfish indoors in fall when the weather turns cold, and store them in an aquarium or a child's wading pool. These small pools come in fiberglass or plastic. If you use the latter, treat it first because plastic residue can be toxic to fish. To treat a pool, fill it with water and add 1 tablespoon of salt per gallon of water. Let it sit for a couple of days; then wash it out and add fresh water. Also, treat tap water with a conditioner. The pH level of your household water should be the same as that of the outdoor water. If the difference in levels is drastic, the shock can kill the fish.

The easiest way to capture fish for transport is to drain three-fourths of the water from the outdoor water garden. With the fish in a more concentrated area, it's easy to collect them with a small net. Place them in a bucket of water. Float this bucket in the indoor aquarium or pool, and let the fish make the move into their indoor home.

Steven Frowine is a horticulturist and an expert goldfish hobbyist.

Photography by Digital Imagery copyright 2001 PhotoDisc, Inc.

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