DIY Pond Filter

The end of summer is a great time of year to make a Do-It-Yourself (DIY) pond filter.

Simple pond filtration system. Via Karen Blakeman/Flickr

The end of summer is a great time of year to make a Do-It-Yourself (DIY) pond filter.  That statement might seem a little counterintuitive since normally, we pond keepers do our planning in the winter and construction in early spring.  But, DIY parts are cheap and some are even free at summer’s end and in early fall.


I always enjoy creating things out of whatever I find around in my fish room or in garden and home improvement centers.  Spending less is always an advantage! The DIY pond filter presented cost about $45 and should be more than sufficient for a 300 gallon garden pond. Of course the sufficiency of filtration depends on the pond’s bioload and the capacity (gallons per hour flow) of the water pump connected to it. Here is a parts list and their sources:

  1. 12 liter (3.1 gallon) plastic, tree sapling pot. Go to a garden center or plant nursery at the end of the summer and ask for a discarded plant pot without holes on the bottom. I was directed out back and found hundreds to choose from.  The garden center was glad to get rid of it for free.
  2. Scrubber sponges (two six-packs) from one of the dollar stores. They cost one dollar for each pack. Make sure they are not impregnated with soap or any other cleaner.

Hardware obtained at home improvement or hardware store:

  • Threaded couplers (2) length, 3.5 x 2 cm inside diameter. Cost $0.70 each.
  • Threaded coupler (1) length 3.0 x 3.2 cm inside diameter. Cost $1.92.
  • Clear plastic, 12-inch, rigid plant pot saucer obtained from a home improvement center. Normally, they cost about $3.50 each but are often discounted at the end of the season. The clear plant saucer will keep debris out of your filter and allow easy viewing to see if the filter needs servicing.
  • Plastic egg crate louvre material.  I used egg crate with a thickness of 1 cm (.375 inch).  You need a 22 cm (8 3/4 in) diameter piece.  Unfortunately, it seems to only be sold in large sheets (116.4cm X 55.6cm) since it is intended to provide protection for ceiling mounted fluorescent lighting. Shop around because there is a big difference in price between home improvement stores. The egg crate sheet used for this filter cost $13. I have plenty left over for my next DIY pond filter. I wish I had thought of this earlier. Checking with a remodeling company might have resulted in some free egg crate material from a renovation.
  • Rigid plastic tube, length 20cm x 2cm inside diameter to be used for the overflow return. Cost $3.
  • Plastic garden hose (male) barb connector, 1 1/2 cm inside diameter. Cost about $2.50.
  • Teflon plumbers tape, 1/2 inch wide. Cost about $1.

Supplies from your local pet store:

  1. Small Bioballs (about 60), 2 1/2 cm size, new cost is about $5 from pet stores.
  2. Large bioballs (about 15), 5 cm size, new cost is about $3 from pet stores.  Pond owners who drop out of the hobby often sell used items on Internet sites specializing in used items. You might find bioballs deeply discounted on one of those sites.
  3. Blue filter pad material, usually sold in 1×2 foot (.348x.6096m) sheets cost about $4. Filter pad is available at local pet shops and aquatic retailers on the Internet.
  4. Silicone aquarium sealer. A small tube costs about $5. I recommend purchasing this item at a local pet shop.  If purchased elsewhere, be sure the packaging states that it is aquarium safe.

I chose to use a 3.0 x 3.2cm coupler on the return side of the filter to ensure the filter properly drains back into the pond.  It is very important to include a filter overflow near the filter’s top. The overflow sends water back into the pond in the event the filter media becomes clogged and fails to pass water through the filter to the bottom drain. A clogged filter without an overflow, resting outside of the pond, could potentially dump all of the pond’s water onto the adjacent ground leaving your fish without water.

The end of summer is a great time of year to make a Do-It-Yourself (DIY) pond filter. 

The filter requires three holes to be drilled for the intake, return and overflow plumbing. See the diagram for details.  Drill your holes in the plastic pot and thread the couplers through the side. Generously apply aquarium sealer on both sides of the pot to make a water tight seal. Allow the aquarium sealer to cure for 24 hours prior to using the filter.

My DIY pond filter is connected to a 600 gallon per hour pump outfitted with a filter screen. The filter screen traps large debris and prevents the pump’s impeller from fouling. The pump rests on a cobblestone on the bottom of the pond.

The filter performs better than expected and hopefully, you will be pleased with the same results. With a little ‘scrounging,’ it is not inconceivable to make this filter for about $20. Enjoy your pond!

Article Categories:
Fish · Ponds and Koi