Can you Convert a Sand Filter for Koi Ponds?

Submitted by Don Harrawood on Fri, 09/09/2016 - 12:37

Sand filters are great for swimming pools, but not so great for a koi pond.  Why is this?  As the fish waste in the water is filtered through the top layer of sand inside the filter, it is kinda like glue and it forms a crust on the surface of the sand bed.  If the filter is not backwashed frequently, the crust gets so thick that the sand filter will not backwash well.   What happens during the backwash cycle then is that water pressure punches a hole through the crust of the sand bed and the backwash water runs through the hole and is wasted.  The sand is not fluffed and washed as it is supposed to be.  At this point, in order to make the filter work properly again, the filter must be opened up and the sand cleaned by hand.  This is a time consuming and rather tedious job.

Some pond supply companies now have offered a solution to this problem.  We are seeing media on the market that replaces the sand and does a marvelous job filtering the water.  We have seen sinking beads, various kinds of plastic media, and light weight materials to replace the sand.  All these do a great job of filtering the water; however there are some problems, mainly in back washing the filter.

When backwashing the filter, without the proper screening, all the media can escape from the filter and go down the drain.  This is because the light weight media requires a screen just below the control valve to prevent the media from escaping the filter during back washing.  Sand filters do not have or require such a screen, and not just any screen will work.  The screen must be small enough to keep the media inside the filter, and large enough to allow all the debris to escape from the filter without clogging the screen during backwashing.  Such screens are not immediately available on the market, and if you find one, it will most likely be heat welded onto the control valve and an expensive control valve must be purchased, if you can find one, in order to get a screen that works..

So should you even try to convert a sand filter for the pond?  You be the judge.

Thanks to Don Harrawood, SKAPA, for this article!


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