How to make an external fish pond filter

Updated March 23, 2017

One of the most important elements of a healthy outdoor fish pond is the filtration system. However, purchasing a filter can be quite expensive and some even fail to do an adequate job keeping the water clean and healthy. Because of this, many fishpond hobbyists choose to make their own filters out of everyday household items in order to keep their ponds healthy without breaking the bank.

Rinse all of your materials thoroughly with warm water. Do not use soaps or any other cleansing agents as this may harm your fish.

Cut a hole into your main plastic container approximately 2-3 inches from the bottom, using the box cutter. This hole will accommodate the PVC pipe that will serve as the outlet for your clean pond water. Next, cut a large hole into the middle of the plastic lid of the container. This hole should be as large as possible as it will serve as the inlet for the dirty pond water to enter the filter.

Cut a 4-inch length of PVC pipe and insert it into the hole you created in the body of your container. Attach it to the container using clear silicone caulking. This will create a waterproof seal preventing dirty water from leaking back into the pond and will hold the PVC in place.

Attach the pond pump to the PVC pipe at the base of the filter using the flexible rubber tubing you purchased at your local hardware store. This process will allow the pond pump to draw water into the top and through the filter.

Cut a piece of mesh window screen large enough to cover the top of your plastic container and attach to the rim of your lid using the same clear silicone caulk you used to attach the PVC pipe with. This will allow the screen to remain taut and stationary once the filter is functioning.

Fill the lower third of the plastic container with aquarium rocks. The rocks should settle in a way that will allow water to pass through them easily. This is the media that will accommodate the beneficial bacteria you need to complete the nitrogen cycle to grow undisturbed.

Fill the next third of the container with filtration media. This material will allow the water to flow through while trapping any floating matter. This media should remain loose in the filter as it will need to be replaced often.

Cover the filter media with the screened lid and then place the filter into the pond at the deepest point.

Turn on the pump and enjoy your clean pond.

Things You'll Need

  • Plastic container with tight fitting lid (the size will be dictated by the size of your pond)
  • Window screen
  • Clear silicone caulk
  • Box cutter
  • 2 inch aquarium rocks
  • Filter media
  • PVC pipe
  • Pond pump
  • Rubber hose (shoud fit over the PVC pipe diameter)
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