How To Create A Bog Filter

Posted by Cathy Green on

In Nature bogs or wetlands are low lying areas in the natural terrain where flora and fauna thrive in a moist environment. In addition to providing a habitat for moisture loving organisms a wetland also functions as a filter for Mother Nature. Using Mother Nature’s Model we can install filters in our ornamental water gardens that are highly effective and natural in appearance. The bog filter is actually a garden that functions as a filter!


  1. Follow the usual directions for building a liner pond. The bog filter portion of the pond should be anywhere from 10-20% of the pond surface. For example if you have a 10’ x 10’ pond equaling 100 sq. ft. the bog filter should take up 10 to 20 sq. ft. of space in that pond. If you plan to stock a lot of fish or Koi err on the larger size.
  2. Using Cinder Block, Stone, Bricks or any other stable building material construct a dry wall to partition off the bog filter from the rest of the pond. We recommend using cinder block (painted black with exterior latex paint) and then “capping off” the blocks with a decorative stone of your choice.
  3. Be sure to run a piece of pipe through the lower portion of the wall that will hook the pump to the pipe work in the bog filter. Put a PVC female adapter fitted with the appropriate sized hose barb fitting to receive the flex hose from your pump.
  4. Install the pump on the opposite side of the pond from where the bog filter is located. This is to facilitate good circulation of water throughout the pond. Select a pump that will turn the volume of the pond over every 1-2 hours. (You can go with a higher flow rate if you wish.)
  5. Next drill the distribution pipe. The outlet of the pump determines the size of the pipes. For example our 5500 gph AquaFlo pump has a 2” outlet therefore 2” pipe is used. The pipe is drilled with 1/4” holes spaced approximately 6” apart. The spacing is an approximate estimate, if there is a long run of pipe; space the holes further apart.
  6. Cap the ends of the pipes.
  7. Next lay the distribution pipe on top of the pond liner in the area partitioned off for the bog filter. Be sure to point the holes at a 45 degree angle toward the bottom. Once you are satisfied with your piping layout, glue all parts together. Gravel bogs that are 2-3 feet in width can be fed by a single course of pipe. Wider areas require additional lines spaced 2-3’ apart. This layout is similar to setting up a septic drain field.
  8. Shovel 3/8” pea gravel into the Bog Filter area but only fill halfway. The construction process is finished, now it’s time to plant your bog! Most gravel is not very clean, wash it as best you can in the wheel barrow but be aware it will muddy up the pond, not to worry it will clear up. After all, that’s what the filter is designed to do!

Planting the Bog Filter

  1. Select your bog plants and arrange them in the bog area that is half filled with gravel. It’s best to plant the tall plants towards the back of the filter, lower growing plants in front. Create interest by contrasting plants with different foliage colors or textures.
  2. After you have arranged the plants to your satisfaction knock the pots off the plants and place the plant with the root ball intact with soil. Do not remove the soil—there is not enough nutrition in a brand new bog to sustain the plants. (Trust us the soil will not wash into your pond.)
  3. After the plants have been placed, gently shovel in the remaining gravel. Your goal is to place the plants at the appropriate level so that when the rest of the gravel is added the gravel level will be above the water level. In other words, no standing water in the gravel filter area.
  4. Turn on your pump and your bog filter is now off and running with years of clear water enjoyment to come.

Common Mistakes

  • Not capping the ends of the PVC distribution pipe, if you don’t do this the water will simply shoot out the ends of the pipe and not through your carefully drilled 1/4” holes.
  • Washing soil off plant roots; if you do this you run the risk of killing your plants, not only will you damage the delicate roots but you will starve the plant as well.

Suggested Plants


Dwarf Horsetail


Assorted Taros

Dwarf Papyrus

Ruby Eye Arrowhead

Blue Carex

Dwarf Variegated Sweetflag

Sensitive Plant

Blue Rush

Japanese Iris

Siberian Iris

Bog Lily

Lizard’s Tail

Spider Lily


Louisiana Iris

Star Grass

Chinese Water Chestnut

Melon Sword

Variegated Spider Lily

Corkscrew Rush



Creeping Jenny

Ribbon Grass


Plants that are Invasive in the Bog (Think twice before planting)

All Cattails

Gold Rush Reed


Aquatic Mint


Red Stemmed Thalia

Chameleon Plant

Mediterranean Reed

Umbrella Palm

Variegated Water Celery

Parrot’s Feather

Yellow Iris

Other Plants (experiment!)



Leopard Plant


Day Lilies

Meadow Rue

Bishops Weed

Forget Me Not

Obedient Plant

Butterfly Gingers

Fox Glove


Butterfly Weed

Ground Orchids

Society Garlic


Hibiscus (not Chinese)


Calla Lily