What I have done is to have my pump in a bucket that has lava rock filling
the bucket and surrounding the pump. The water is pumped into a liner that
you can get at Home Depot which is meant to line a half oak barrel. It has
a lip on the rim for water to flow out of (which goes back into the pond
where it is pumped from). I grow my plants in this and it has worked very
well as a filtering system. The only work that has to be done is the plants
must be thinned on occasion since they really do flourish in this type of
set up and I have actually had the roots become such a solid mass that the
water cannot flow in and out properly without thinning. I have forgotten to
rinse out my bucket which as the lava rock for as long as two years without
any problem. As inexpensive as lava rock is you could just replace it every
year if you could not manage to do the work of cleaning it but you would
still need to get it in and out of the pond eventually.

Given that this works for me very well and sounds similar to what you are
proposing, your plan may work but I have never heard of a bottom drain
system. I would think that you might have a problem with getting really
clean water from this type of system and that you would have a build up of
gunk that had to be dealt with. I would think you would want the water
pumped in to be a very low flow rate... I don't know... just guessing on
this.


"GrannyGrump" wrote in message
...
I am disabled, and can't clean filters easily, so I am planning on
making a veggie filter from a large water trough (Tractor Supply).
Planning on rocking this in, with a roof, so that it looks like a
wishing well...
This trough has an opening at the bottom for draining water.
I am planning on having water pumped from my pond into the top, so
that it trickles down to the bottom and back into the pond.
I figure lava rock on the bottom, then a layer of gravel, then a layer
of barley straw, with water cress and water plants on top.

Will this work?