I decided it was a good day to clean out two of our three berm veggie
filters. They had not been touched since a little over a year ago.

The first one is a 4 x 4 x 18" unit that thats 45 min to fill. The
water slowly enters at one corner to make a circular (think vortex)
flow. The water exits 270 degrees from the entrance at the top of the
filter. The water celery has totally filled the box.

The second comes after the first and is a 4 x 8 x 18" unit. The water
goes in one end and out the other end, 8 ft away. There is a slight
vortex action in this box as well.

I started with the long filter. After a season, it had about 3 inches
of muck and dead hyacinth in it. Pretty good, I thought. Hyacinth
roots did their thing.

Then I started on the smaller one, into which the water runs first.
The top was entirely covered by water celery, standing 15 inches above
the surface. When I began to pull the celery, The roots were covered
with very thick muck. As I pulled it out, it became clear that the
ENTIRE filter was filled with muck so thick that it was like gravy
rather than water. It was amazing. The first unit got almost all of
the muck from the pond!

My conclusion: thick plant roots really do their thing.

Jim