How to Make a Biological Pond Filter
Ponds contain a complex ecosystem of plants, fish and other aquatic creatures. Plants filter out some contaminants in the water, however, for a healthy pond you will need to invest in a filter. The least expensive, and easiest to maintain is a biological filter. Biological filters consist of biomedia which provides a home for bacteria, a pump to move the water, and a container to keep everything together. Biomedia can be plastic balls, rings or hair curlers, or it can be rock or gravel. Bacteria naturally occurring in the pond water grows on the biomedia. Water is forced over the biomedia, allowing the bacteria to trap and feed on debris that would make the water cloudy and unsuitable for fish and plants. Large debris, like leaves, needs to be removed by hand using a skimmer. Biological filters are cleaned twice a year. You just need to wash the container, pump and biomedia with water and reassemble. Does this Spark an idea?
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Things You'll Need
- Container
- Drill
- Biodegradable furnace filter
- Knife or scissors
- Mesh bag
- Plastic balls, rings or hair curlers
- Underwater pump
- Piping
- Rocks or gravel
Instructions
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1
Estimate the size of the pond. You can use the formula length x width x average depth x 6.23 for a rough estimate, or, use the links provided to determine a more accurate measurement. Use the estimate to determine how big the filter needs to be and how much biomedia you will need.
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2
Use a sturdy metal or plastic container big enough to hold the biomedia and pump, pails or plastic milk crates work well. If you select a pail you will need to drill 1/4 to 1/2 inch holes in the sides and bottom. Drill one hole big enough for the power cord to the pump to fit through.
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3
Cut the bio-degradable furnace filter to fit into the container. It's easier if you cut pieces to fit the bottom, each of the sides and the top. For a pail, you can curl the furnace filter around the sides. Cut a hole in the top piece of furnace filter large enough to fit the outlet pipe through. Cut a hole in the side piece big enough to feed the pump's power cord through. Line the bottom and sides with the furnace filter, being careful to orient the hole for the power cord in the furnace filter with the hole in the container.
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4
Place the plastic balls into the mesh bag and put it in the bottom of the container.
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5
Fit the plastic pipes to the pump according to manufacturer's directions. Place the pump on top of the plastic with the inlet pipe facing the plastic and the outlet pipe coming out of the top of the container. Feed the cord through the hole in the furnace filter and container.
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6
Fill the container with medium size rocks, gravel or volcanic rock.
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Place the top piece of furnace filter on the opening of the container.
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Place the biological filter in the bottom of the pond. Choose a spot that is not readily visible.
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Tips & Warnings
Use a matte-colored container to minimize its visibility. Use a filter slightly larger than what you think you will need. Put your filter in the pond in spring after any ice has thawed, and remove it in the fall before the water freezes. The better balance you have between fish and plants in your pond, the less work your filter will have to do.
Clean you biological filter twice a year (early summer, then again when it's removed) for best results. Only use a biodegradable furnace filter, a plastic one may release chemicals as it ages. Replace the biodegradable furnace filter every two years, or when it starts to look worn.
