How to build a koi pond filter!

Building a pond filter is a relatively easy task.  The goal is to change the water 10-20 times an hour while keeping most of the big stuff trapped in the filter.  The filter is a biological master piece.  It is a good thing we do not need to know the details.  We just need to have plenty of room for the good bacteria to hang out and do their thing.  Look at the pictures below.  The first 6 pictures are pond and fish pictures.  The plant shelf behind the fish is 24 inches long.  Notice the cup with soaking fish food in the sixth picture.  If you soak your fish food for 20-30 minutes before feeding the fish, they digest the food better resulting in less waste being generated.  Less waste, means less pond cleaning.  Pictures 7 & 8 show the difference between tap water and pond water.  The pond water on the right is supposed to be dirty.

The second row of pictures is the materials used to build the filter.  The materials are the type of stuff that most pond owners collect becuase there may be a need for it some day.  The 50 pound bag of carbon can be found at a local GE/Ionics water supply store for about $30.  If you don't feel like tracking the local water supply store down, you can buy a 5 gallon bucked off ebay for around $30.  I got most of my stuff from a local drug manufacturer.  They generate a lot of waste because of their standards.  The 4th and 5th pictures show the roof gutter that I used for water return.  The 8th picture shows a piece of downspout with a whole bunch of holes drilled in it.  The holes are to keep the fish from getting sucked into the pump intake.

The first picture on the third row shows a 5 gallon bucket, half full of small stones, sitting in the middle of a 50 lb bag of carbon at the bottom of the barrel.  The stones are to break up the water current from the pump.  I don't really want to disturb the carbon at the bottom.  I want it there to hold bacteria and remove the chlorine.  The next picture shows how I inserted the intake pipe into the home made intake guard.  The third picture shows how I use two pipes into the stones to spread distribute the water across the stones.  The valve in pictures 3 and 4 is to control the water flow into the filter.  Too much water into the filter can result in a spill over the sides of the filter.  Picture 6 dipicts the good old fashioned hot glue gun to glue the gutter to the drum.  I was told to buy all of this expensive fish friendly glue but the hot glue does not seem to have any adverse affects on the fish.  The 7th picture is a feeding frenzy.  The eight picture shows the filter media raising up much higher than I anticipated.  This had to be corrected by removing some of the floating media and intalling a tie bar to prevent the media from covering the overflow pipe.

Make sure to remember that ponds are living things and require time to adapt.  The water should always be to dirty to drink.  Koi fish like to swim in currents.  I change the currents regularly.  Do not clean the filter often.  The filter can smell bad.  The water should not smell bad.  Never change more than 20% of the water per week.  I do about 10 water changes per year of about 20%.  UV lights are very helpful in keeping the water clear.  There is no getting around the $100 for the UV light.


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This type of filter is an up flow style where the debris stays below the filter media.  AFter the filter is built and running, you can surround it with T-11 siding or painted wood for aesthetics.
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