ask This Old House
How to maintain a pond
We have a small man-made pond on our property that fills every year with pine needles and other stuff, creating a very mucky bottom. In the last few years, it has developed a duckweed “cover” that appears in midspring and lasts until late fall. What can I do to keep the water clean?
—THOMAS PETRO-ROY, CHELMSFORD, MA
TOH landscape contractor Jenn Nawada:
In the natural environment, the accumulations of organic matter that contribute to the growth of algae and duckweed in ponds are flushed out by spring rains. Man-made ponds don’t have the benefit of such regular cleansing, so you’ll need to give yours some TLC at least once a year.
If you have fish living in your pond, do not resort to using chemical herbicides to get rid of duckweed: They are toxic to fish and other wildlife. Instead, transfer fish to a large tank with a bubbler to keep the water well oxygenated while you clean your pond.
Begin by scooping out the debris from the bottom by hand, then drain the water out with a submersible pump. When the pond is empty, remove any remaining debris and power-wash the stones that line the pond.
At this point, you have a good opportunity to install a two-stage pond filtration system, like this one by
