A pond filter is a vital component for any outdoor or indoor garden pond. Filters provide biological and mechanical filtration, pushing water through a filter medium and expelling cleaner water free of ammonia or any other waste from plants or koi. A good filter not only keeps water healthy but also keeps it clear. Pond filters range in price from a hundred to several hundred dollars, but you can build your own with a trip to the hardware store that is just as effective.
Cut several dozen holes in the side of the plastic waste bin using a power drill and a 1-inch hole-cutting drill bit. These are the holes that the water passes through when filtered.
Place a 2-inch thick layer of pebbles at the bottom of the waste bin. The pebbles weigh down the filter and provide surface area for beneficial bacteria.
Place a layer of plastic balls over the pebbles. The balls provide more surface area for the beneficial bacteria to grow.
Fill a nylon bag with activated carbon, which can be purchased in cartons at hardware stores, and tie it shut. Place the bag of carbon over the plastic balls. The carbon helps neutralise odours and harmful chemicals in the water.
Fill the remainder of the wastebasket with filter floss, which traps large particles that pass through the filter, and put the lid on tight.
Seal one end of the PVC tubing to one of the holes on the filter you made using aquarium sealant. Allow at least 24 hours to dry.
Attach the other end of the PVC tubing to the input tube of the pond water pump. This is where the pump takes in water. Attach the two tubes using a tight-fitting rubber coupling. There should be about 6 inches of space between the filter and the pump, so you may need to cut the PVC tubing with the utility knife.
Submerge both the filter and the pond pump in the centre of the pond and power on the pump. Water should begin sucking through the filter where it is cleaned and then expelled through the pump back into the pond.