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?