Winterizing the aquatic garden now will help ensure that fish and plants get off to a healthier start in the spring.
As the days grow shorter and water temperatures drop, plants end their growing season and begin to yellow or die back, even before their foliage is killed by frost. Hardy fish undergo metabolic changes that enable them to survive several months of frigid temperatures - with a little help from the savvy pond keeper.
Simply stated, fat fish in clean water are key to the winter survival of pond life.
As temperatures begin to drop, koi, goldfish, orfe and other cold-hardy fish need to gain body fat that will sustain them through winter. Generally, halt hand-feeding when the water temperature in the pond reaches 50 degrees, according to Charles B. Thomas, chairman of Lilypons Water Gardens and author of three books on aquatic gardening.
"During the summer, we feed fish a high-protein food, but for fall, we need to decrease protein and increase carbohydrates to build body fat," Thomas said.
In cold water, fish enter a semi-torpid state, rarely venturing from the warmer water at the bottom of the pond. During this time, they are unable to metabolize food, and continuing to provide it puts them at risk of fatal digestive-tract disorders.
Tim McQuaid, aquatics manager at Valley View Farms in Cockeysville, says switching to a vegetable-based fish food when the water temperature reaches 52 degrees will allow the pond keeper to continue feeding fish until the temperature drops to 42 degrees.
Specially-formulated foods for fall and spring are available at aquatic garden centers and most pet stores. A pond thermometer also is a wise investment.
Providing oxygen and clean water through the winter is essential. Leaves and other organic matter decaying on the pond bottom rob the water of oxygen and produce toxic gases that can be fatal to fish.
To prevent a buildup of fallen leaves, place netting over the pond to catch debris. Be careful not to let the net dip into the water where fish can become entangled. Stake it well above the water surface, but let it drape over the sides to keep leaves from blowing into the water from below.
Fall also is the best time to give the pond a thorough cleaning to remove silt and organic matter that may have accumulated on the bottom. Every few years, when buildup is 2 to 3 inches deep, the pond should be drained, scrubbed and refilled.
"Fish are at their best in the fall," McQuaid said. "They're fat and healthy, and they can withstand the stress of being moved. In the spring, they've used up their fat - they're weak and more fragile."
Some of the pond water should be pumped or bailed into a temporary holding tank in the shade. (A child's wading pool will do. Place a net or screen over the tank to prevent fish from jumping out). An aerator or pump should be placed into the holding tank to keep water oxygenated.
McQuaid recommends draining the main pond until the dorsal fins of the fish are above water. Netting them out is easier at this fTC point, and perhaps is less stressful for the fish than being chased around a half-filled pond. Use a plastic bag or bucket of water to move them into the holding tank.
After the pond is cleaned and refilled, treat it with a commercial water conditioner to remove chlorine and other additives and to neutralize heavy metals. Thomas also recommends adding one pound of pond salt to every 100 gallons of pond water to enhance the health of fish.
"Going into and coming out of dormancy causes stress on fish," he said. "This is the time when bacteria or parasites can get the upper hand. Fish have a protective slime coat, and salt helps to maintain that. When there is no salt in the water, fish lose some of their own body salt to the water through osmosis, and it makes them vulnerable to disease and parasites." Do not use table salt in the pond, Thomas stresses.
To acclimate the fish to their cleaned pond, drain half the water out of the holding tank and refill it with fresh water.
Temperature shock is the most common killer of fish during pond cleaning, according to Thomas. The newly cleaned pond should be within 3 degrees of that in the holding tank. If it is not, slowly add fresh water to the holding tank to equalize the temperatures.
As freezing temperatures set in, a floating de-icer is essential for keeping an opening in the ice cover to allow the exchange of oxygen and toxic gases. Never attempt to break ice with a hammer or ax. The shock wave traveling through the water can injure or kill fish.
Running the pond pump and fountain may keep water moving and prevent freezing, but it also brings warm water from the depths of the pool and exposes it to frigid air. The result is that the overall temperature of the pond is lowered.
Lilypons plans water-gardening lectures at its Buckeystown facility. Sessions are set for 1 p.m. and 2 p.m. Oct. 11, Oct. 24 and Oct. 25. Visit its Web site at www.lilypons.com.
Caring for aquatic plants
Preserving hardy and tropical aquatic plants through the winter is a simple task. Keep hardy plants in the water garden as long as possible, removing only dead or dying foliage.
* Hardy aquatic plants. As soon as they are top-killed by frost, cut back to just above the water level. Pots should be left in the water.
* Hardy water lilies and lotuses. Cut back to within two inches of the root and set the pot on the pool floor if there is a chance that the pond will freeze to the depth of their crowns. If the pond is too shallow to prevent ice from damaging the crowns, remove pots from the water and store in a frost-free garage or basement. Wrap plants and their containers in damp newspapers and drape them with plastic. Do not let plants dry out.
* Tropical aquatics. Taro, papyrus, umbrella palm and others easily adjust to life as house plants. Bring them indoors before the frost and place them in a sunny location. Keep soil damp through the winter, or place the entire pot in a larger container of water.
* Water hyacinth. This vigorous, free-floating tropical bloomer, usually grown as an annual, can be overwintered indoors. Place soil in the bottom of a container of water. As long as the plant's trailing roots can touch the soil, it will extract nutrients and remain green.
Pub Date: 10/11/98