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building a bog filter

18 years ago

My pond is 9'x12' and 20" at its deepest part. I live in the sunny south and there is no shade around the pond. I am working on building a bog, not for vegetation, but to put lava rock in the bottom and run the tubing from the pump in the pond around to the back and into the bottom of the bog and use the overflow to feed a waterfall into the pond proper. I just can't get a picture of how to do this. I can visualize how to do a water fall. But that is because there are all kinds of instructions on how to do them. Can anyone talk me through this and warn me of possible errors I might make. Thanks

Comments (5)

  • edbyrnes
    18 years ago

    Hello Oldone!

    I will tell you how I would build the filter you are talking about. The filter itself has to be higher than the waterfall and the waterfall must be higher than the pond since gravity more or less directs the flow of the water.

    It sounds like you have plenty of room so once you have placed enough soil behind and above your waterfall so that the filter pool will be higher than the waterfall and pond you can dig any shape for the filter. You will want to really tamp down the soil in the area you will dig, maybe let it settle with rain or a sprinkler and tamp some more.

    The minimum size for the filter for the pond you describe should hold 100 to 150 gallons of water, I know there are ways to calculate this but I would dig a hole 2 feet deep and about 4 feet in diameter.

    Depending on the type of soil you are working in, you may want to line the hole with old carpet or foam padding so that sharp things don't poke a hole through the EDPM rubber liner you will place in the filter hole.

    Then fill the filter pool with water and try to level things out all the way around the filter. Build in a low area right behind the waterfall so the water will flow down into the waterfall. Be sure your EDPM is wide enough at the waterfall end so that it overlaps into the waterfall pool otherwise it is easy to lose water between the filter and the waterfall.

    Then use PVC around 1 inch in diameter to build a pipe from the center bottom of the pool to the side and up the side to the surface. You may want to anchor it in place with some rocks. From here you bury flexible clear tubing down along the filter, the waterfall, and to the far end of the pond. Now you hook the tube to a submersible pump that pushes 75 to 140 gallons per hour.

    Fill the pool to about six inches from the top with your lava rock. All the pores in that rock will harbor billions of filtering bacteria. Some lava rock is sharp so watch the liner.

    Now you should have a pool with six inches of clear water and 18 inches of lava rock. With the pump on, the water seeps through the lava rock and out to the waterfall. After a few days your pond becomes almost crystal clear.

    If I were doing it, I would decide to add plants to the filter pool. I would start by just setting pots with pitcher plants and other bog plants right onto the lava rock. Once the top of the pool was fairly well filled with plants I'd place the taller toward the sides of the pool filter, the smaller toward the middle. I'd keep it clear in front of the waterfall.

    So there is my idea of how I would do it. Perhaps others will make suggestions, which will further improve the filter.

    The best of luck,

  • TREESA207
    18 years ago

    Hello Oldone,
    Do you happen to live in Hendersonville?

  • gardensareme
    18 years ago

    Hi there, check out this site, we used and and our imagination, (added a bottom drain) ....

    jane * kevin

  • edbyrnes
    18 years ago

    The link should be:

    Hey Jane and Keven...excellent collection of how-to's, I will be visiting that page often. Glad you put it together.


  • ncpeace
    18 years ago

    Hello Ed, wonderful instructions and so much appreciated. I think my answer is that it is really impractical to attempt such an undertaking in part sand and part clay soil. I think I will just use my mountain to make a waterfall and call it a day. A really hot day this time of year. Again, I appreciate so much your time and great instructions. I changed from "oldone" to "ncpeace".