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Pond Troubleshooting

Wedels - Lotus FlowerGreen water

Green water is an algae bloom and can be a symptom of many different problems. Overfeeding, too few plants, too many fish, insufficient filtration or aeration, surface runoff, too much sunlight or water changes can contribute to green water. If you can determine which of these is the primary problem and correct it, the algae bloom should stop. In many cases, pond owners are unwilling to change what they are doing. For those people, a variety of tools and products can minimize the effects of an ecosystem imbalance. Phosphate-consuming bacteria will help deprive algae of its food source. Some resins absorb phosphates. Decomposing barley straw acts as a pre-emergent algae control. Chemical products cause algae to coagulate so it can be physically removed from the pond. Water dyes can reduce sunlight penetration to reduce algae growth. Ultraviolet sterilizers bleach the algae, eliminating the photosynthesis. Keep in mind that the use of these tools and products will probably have to be continuous because you are treating only the symptom and not the cause of the problem.

Here are the most common causes of pond imbalance. Learning to determine which are contributing to your pond problems help make it possible to eliminate the source.

Not enough plants

There are three general classifications of water garden plants: floaters, marginals and oxygenators. The surface of a pond should be about 60 percent covered with plants. A combination of floaters and marginals can be used. Plants in a water garden garden have many functions. They are nature’s filters and remove nutrients from the water, reducing algae growth. They help shade the water and minimize temperature fluctuations, which can be detrimental to fish. Plants also provide hiding places and are food source for the fish.  Oxygenating plants help add oxygen to the water.

Not enough aeration

Aeration helps add oxygen to the water. A natural exchange of gases on the surface of the pond occurs with the atmosphere. In a pond that is overstocked with fish or has a high organic content, oxygen depletion can occur. Fish will be sluggish and at the surface gasping for air. This is a sign that the natural gas exchange is not enough. By turning the pond water once every two hours, you can replenish adequate oxygenation. The water can be pumped over waterfalls, through fountain heads or spitters to achieve this aeration.

Poor filtration

In a well-balanced pond, filters are not always necessary, but filters help reduce problems in many situations. To basic types of filters are used in water gardens: mechanical and biological. (One half of the water should be filtered every hour.)

Mechanical filters collect debris that falls into the pond and remove solids from the water. Filters also help keep pumps and fountain heads from clogging. Mechanical filters are generally submersible or skimmers. Biological filters can perform the functions of a mechanical filter, but also contain a chamber for bacteria to grow. These bacteria convert toxic ammonia compounds into nitrates and then nitrates that are used by the plants.

Debris and sludge buildup

Leaves, grass clippings and other things ca fall or be blown into the pond. This debris is unsightly and should be removed. A pond skimmer incorporated into the pond will eliminate this problem or you can net the debris and remove it. Pond netting can be placed over the pond to catch leaves.

If this debris is not removed from the pond, most of it will sink to the bottom and contribute  to sludge buildup. Fish waste, excess fish food and pond plant parts also contribute to sludge. Bacteria in the pond will break down the organic material into sludge and then into ash. In many ponds, the process is not complete and the sludge builds up. The accumulation of sludge should be removed at least once a year.

Frequent water changes

Whenever the water in the pond is changed, keep in mind that the new water is loaded with nutrients, which can lead to algae growth. It is natural for a pond to turn green within a couple of weeks of filling. Many people panic at this time and refill the pond. This only allows the green cycle to repeat. Usually four to six weeks after the initial filling the nutrients present in the water are depleted and the water will clear. If city water is used, it is best to treat the water to remove chlorine and chloramines to prevent harm to fish and plants.

Too many fish

Fish will grow and multiply in a water garden. For goldfish and other common pond fish, you should have a minimum of 3 gallons of water per 1 inch of fish. Koi are bigger and messier fish, so I would recommend 100 gallons of water per fish. To determine the volume of water in the pond, use this formula:

Length x width x depth (in feet) = Number of cubic feet of water in the pond

Then convert to gallons by multiplying the result by 7.48 (1 cubic foot = 7.48 gallons). Fish waste includes ammonia, which can build to toxic levels. Too many fish can also lead to an oxygen shortage in the water. Biological filtration can be used to decrease ammonia levels and increased aeration will oxygenate the water. If this cannot be done, reduce the number of fish.

Overfeeding the fish

Many pond owners have named every fish and feel that their fish need to eat whenever they themselves eat. Every time they go out to the pond, the fish seem to be hungry. Fish do not need to be constantly fed. Feed the fish no more than once per day and then only give them what they will consume within minutes. The more the fish eat the more waste they produce.  Any excess food and fish waste can contribute to algae growth and to organic sludge buildup in the pond. When the water temperature is below 55 degrees, the metabolism of the fish slows down and all feeding should stop.

Drainage into the pond

Unfortunately, some ponds are located at the lowest point in the landscape. Some people think that because the water gathers at that point naturally, it is the ideal spot for a water garden. Surface water drainage into the pond can carry debris, soil, nutrients and even pesticides. This can lead to cloudy water, algae problems and in some cases, fish and plant kill. To stop these problems, it is best to raise the pond or create a dike to divert the surface water.

Failure to winterize

In climates where the surface of the pond will freeze, it is best to do a little preparation. Stop feeding fish when the water temperature falls below 55 degrees. Any sludge or organic waste material should be removed from the bottom of the pond. Hardy plants should be cut back and placed on the bottom of the pond. Annual plants should be discarded. External filters should be cleaned and drained. These simple precautions will minimize winter damage to your pond and its aquatic life.

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