How to Build a Bog Filter System for Fish Ponds
Every pond, no matter how small, needs some type of filter to maintain a healthy ecosystem. Bog filters, also known as veggie filters, give pond owners a chance to experiment with "in between" plants, vegetation that likes wet feet but does not like standing water. Flag irises, horsetails, spider lilies, creeping jenny and ribbon grass are just a few of the plants that will thrive in bog filters. Does this Spark an idea?
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Things You'll Need
- Shovel or backhoe
- Plastic pond liner
- Cinder block, stone or brick
- Pump
- PVC pipe sized to fit your pump
- PVC female adapter with hose barb
- Drill with 1/4-inch bit
- PVC cap
- PVC glue
- Gravel or lava rock
- Plants
Instructions
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Building a Bog Filter
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1
The bog filter should be 5 percent to 15 percent the size of the water volume in the pond. To determine the cubic feet of water in the pond, multiply length times width times the average depth. Multiply the cubic feet of water by 7.48 to find the minimum size for the bog filter and the pump.
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2
Dig the bog filter in the narrow end of the pond. The bog filter and pond should share a side. The bog filterbottom should be higher than the bottom of the pond and as wide as the pond.
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3
Line the hole with plastic pond liner. You also can use a plastic kiddie pool or shallow stock tank. Dig the hole to fit.
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4
Build a "dry wall" -- no mortar needed -- between the filter and the pond. Stack the bricks, concrete blocks or stone until they are level with the top of the sides of the bog filter.
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5
Place the pump in the pond on the side away from the bog filter. Choose a pump strong enough to circulate the volume of water in the pond every two hours. Follow manufacturer's directions to set up the pump.
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6
Fit PVC pipe to the outlet hose of the pump using a female adapter with a hose barb to connect to the pump outlet. The PVC pipe needs to be the same size as the pump outlet.
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7
Run PVC piping from the pump around the pond to the far end of the bog filter. Run the pipe over the side of the bog filter and down the inside until it touches the bottom. You can bury the PVC piping under the pond and bog filter for a new installation or along the side of the pond and bog filter for an existing pond.
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8
Drill 1/4 inch holes along one side of a PVC pipe. Connect the drilled PVC pipe to the PVC pipe running from the pump with the holes at a 45 degree angle to the bottom of the bog filter. Cap the free end of the distribution pipe. Use PVC glue to secure the pieces of PVC.
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9
Gently fill the bog filter with gravel, stone or lava rocks until it is halfway full or until the gravel puts the plants are at the right planting depth.
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10
Arrange your plants, with the containers removed but the soil still around the root balls on the gravel.
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11
Fill with remaining gravel, stones or lava rock until the plants sit above the water level of the bog filter.
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12
Cover the edges of the pond liner with large stones or pavers.
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1
Tips & Warnings
For large ponds you may need more than one distribution pipe. Lay multiple distribution pipes out in the same pattern used for septic drainage fields. Any plant that likes wet feet will work in a bog filter. Place the bog filter so that it will receive at least 6 hours of direct sunlight a day. The bigger your bog filter the more plants and fish you can have.
Avoid invasive plants as they can move into your pond. Avoid placing your pond and bog filter in the path of water runoff from septic fields, and hard surfaces (like sidewalks, driveways and roads).
