University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article


By Dr. Leonard Perry, Extension Professor
University of Vermont

Spring cleaning is an annual ritual in most homes. But it's a necessity outdoors, too, if you have a water garden in your yard to prevent murky water caused by buildup of algae bloom and plant debris.

The American Nursery and Landscape Association recommends evaluating the cleanliness of your water garden after spring thaw occurs. If you have been diligent about pruning plants and skimming, you'll only need to drain the pool or pond every three to five years. Never drain it more than once a year, however, and always when temperatures are below 70 degrees F.

Depending on the amount of decomposed debris, you probably can use a net to clean small pools. For larger ponds where a lot of debris has settled at the bottom, you will need to pump the water out with an existing, submerged pump or by siphoning. Transfer most of the old water to a clean garbage can, children's wading pool, or large buckets.
As you lower the water level, carefully remove the plants. Keep them moist and out of direct sun. If you have fish in your pond, pump the water level down to about six inches, then catch them with a net. Put the fish in holding containers of the "old water," covering these with netting to discourage predators and prevent the fish from jumping out.

Once the pond is empty, quickly rinse the walls. Try to leave most of the algae as this assures a healthy pond environment. Use a wet/dry shop vacuum to remove every last bit of water. Then refill with clean water, adding a neutralizer chemical to hasten dechlorinization.

Replace the plants, giving those that need it a quick trim first. When the water temperature stabilizes, you can return the fish to the pond. There should be no more than three to five degrees difference in temperature between the old and the new water to prevent shock to the fish.

It's a good idea to add some hiding places for fish and frogs in the pond as a guard against predators. Pond walls that slope straight down from the sides, as opposed to gradual slopes with shallow areas which wading birds like also help prevent predators from cleaning out your fish as does placing an owl or heron decoy near the pond. Move it often.

Plants will keep water clear as they absorb the nitrate buildup that naturally occurs in ponds. However, throughout the summer, you will need to regularly prune plants both to control algae and enhance the appearance of the water garden. Periodic skimming and netting also will keep your water feature attractive and cut down on spring cleaning next year.

Encourage nature's cleaners--tadpoles and Japanese black snails--to live in your pool or pond. Tadpoles will eat waste before it turns into nitrate. The snails love algae but won't bother your plants. However, if there is too much debris or too many fish, neither critter can do an effective job.

To maintain clean, clear water you also can rely on mechanical and biological filters and ultraviolet lights. These are available at many garden centers and nurseries or can be ordered on-line.

Follow these steps and your water garden will be a beautiful asset, and not a hindrance, to your landscape. Happy spring cleaning!

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