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Understanding how to maintain a perfect pond

By Veronica Lorson Fowler

The pond owner's nightmare goes something like this: Ropy algae that refuses to go away, water levels that refuse to rise, and a mess of dead fish that make it look as though someone dropped a bomb.

"A pond is a living ecosystem," says Eric Norland, an Extension specialist in pond management at Ohio State University. "There is no single right way to manage a pond and no one wrong way."

The key, says Norland, is to decide what you want out of a pond and how to get it. If repairing that sagging outbuilding or building a patio is taking up all your time, it's perfectly OK just to let the pond go and let it do whatever it wants. Yes, you'll probably get a lot of algae and pond weeds, and any fish that survive won't be particularly desirable, "but it will be a very natural pond."

At the other end of the spectrum is the highly managed pond, with clear water, a perfectly balanced fish population, and an abundance of other wildlife. However, Norland warns, anyone who wants crystal-clear water "should invest in some concrete for an in-ground pool." Pond water will always have a greenish cast from phytoplankton, part of a healthy pond.

Maintain the banks

Beyond controlling algae and pond weeds, water can be kept fairly clear by making sure the banks are well planted (trees are ideal, but grass is also very good) to prevent erosion. Also, cattle should not be allowed access because they ruin bank slopes and nearby sod and their waste pollutes the water. If your home has a septic tank, you'll want to make sure wastes don't seep into the pond. You can further assure some degree of water purity by controlling runoff with diversion ditches, tiling, embankments, and grading.

Muddy water can sometimes be treated by applying ground agricultural limestone, agricultural gypsum, or commercial alum, cottonseed meal, superphosphate, and even hay. However, check with your Extension service first to determine the source of the problem.

If the water is reasonably clear and smells fairly good, it's almost certainly fine for swimming, says Norland. If you're concerned about the presence of pesticides, tests are available through your county Extension service, "but you can go broke testing for all possible pesticides," he says. It's best to limit the tests to a handful of the most likely pesticides used in your area.

Animal wastes can also be a problem. For that reason, it's recommended that a pond used for swimming not have more than one pair of domesticated ducks or geese.

The best fishing is in ponds greater than 1 acre where overfishing presents less of a problem. Ponds can be stocked with fish from private dealers or your state department of natural resources. Trout need ponds where water temperatures don't exceed 75° to 80°, but large-mouth bass, channel catfish, bluegills (redear sunfish), and hybrid sunfish do well in warm pond waters. It's usually not necessary to feed fish.

The average depth for best fishing in a pond 1 acre or larger is 6 to 8 feet with a maximum depth of no more than 12 feet. It's tough to control fish populations in a stream-fed pond, where the stream brings along fish from the outside, but in a watershed pond, you can periodically seine to both check your fish population and correct it. You can also control populations by setting limits on size and type of fish and by setting fish traps.

Create an underwater shelter

As long as you fish regularly in your pond, "You can get a pretty good idea of the health and fish population," says Stratford Kay, aquatic specialist at North Carolina State University. To help fish breed and survive, create an underwater shelter in your pond. This will also concentrate fish for easy fishing.

Brush piles of evergreens (including old Christmas trees), beds of wooden stakes, and even slashed and bound automobile tires all work well.

Small ponds often have problems with oxygen depletion. An aerator made specifically for the purpose will help oxygenate the water and will have the side benefit of keeping water open during the winter, helping fish survive.

Fountains are often believed to aerate the water as well as control algae. However, their contribution to those objectives is minimal.

Wildlife is a large part of the pleasure of a pond. A large body of still water attracts quail, rabbits, raccoons, turtles, songbirds, ducks, and deer. You can increase wildlife populations by providing plenty of cover in the form of grasses, trees, and shrubs, especially those that bear small fruits. Large clumps of evergreens nearby will provide winter cover. And predator-proof duck boxes will encourage wood ducks in most areas.

Wildlife can also be the undoing of a pond. Canada geese can create a nuisance with droppings, while muskrats, groundhogs, and beavers can dig into dams, compromising the stability of the pond, and do other burrowing damage.

Your local Extension office will have recommendations for trees and plants that thrive alongside ponds. Nearly any tree that doesn't drop excessive fruit (such as some crab apples) is fine. Willows are a classic choice, but can spread rapidly and become a nuisance.

A number of aquatic perennials also are lovely and do well either right alongside the pond or in areas a few inches deep, including most yellow flags, Louisiana irises, calla lilies, cardinal flower, and various rushes. Water lilies, a wonderfully romantic pond plant, are also beautiful, but in warmer climates they can overtake small, shallow ponds. Most water lilies do best when planted in pots set on the pond's bottom 1 to 2 feet deep. Cold hardiness of water lilies varies radically, so read labels carefully.

Heed these cautions

Be careful if planting rapidly multiplying plants sold for water gardens, especially water hyacinth and parrot feather. These plants can escape into the wild and overrun natural waterways.

Also, plants bought in garden centers may contain other unwanted, invasive plants tucked in among the leaves, such as duckweed, mosquito fern, salvinia, and hydrilla. These little plant hitchhikers can overrun small ponds.

Soil types, pH levels, aquatic weeds, fish, and rules and regulations all vary widely by state. What works (or is allowed) in one state may not work in the next. Contact your state or county Extension service for loads of free or low-cost information on pond management.

Always keep a life buoy and long pole mounted in a clearly visible place near your pond to prevent drownings. It's also important to keep the pond free of trees, stumps, and brush that might be a hazard to swimmers. For the same reason, trash, bottles, and cans should be cleaned up. It's also smart to establish clear rules for swimming and boating on the pond to prevent any problems.

A pond can be a beautiful asset to your property and a source of great pleasure. It takes a bit of research and work to keep it attractive and clear, but it's well worth the extra effort.

How green was my pond

Algae, especially the ropy filamentous algae, is probably the biggest problem for pond owners, says Stratford Kay, North Carolina State University aquatic specialist. This problem is followed closely by duckweed and duckweed-like floating weeds.

The most effective thing you can do to control these problem plants is to control the amount of fertilizer and nitrogen that washes into the pond. It's best to avoid using fertilizer at all on the watershed for the pond. If that's not possible, don't fertilize on at least a 40- to 50-foot area surrounding the pond.

Other tips for controlling algae and weeds:

  • Do not keep livestock on the surrounding watershed. Check with neighbors who may be fertilizing the watershed. Excess nitrogen is a leading cause of algae and weed problems.

  • Make sure the pond has an average depth of at least 3 feet (6 feet is better) to discourage the growth of water weeds.

  • In small areas where rooted plants are a problem, simply pulling them may be sufficient. Scooping out algae and floating plants is usually not effective.

  • Triploid grass carp may be introduced to eat submersed weeds; however, they are banned in some states so check before stocking.

  • If the problem is severe and chronic, you may want to consider chemical control. However, chemicals treat the symptoms rather than the problem. If possible identify and remedy the root cause of the algae and weeds.

  • If your pond is larger than 1 acre and equipped with a drainpipe, you may want to do a winter drawdown. Drain the pond by one third to one half from November until March to expose submerged aquatic plants to freezing and drying. This works only in climates where winters go down to 20 degrees or colder for at least three months. This is a dramatic step, so check with your county Extension office first.

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