One of our berm ponds (4 x 8) has small fish in it and needs a clean
out. The usual process is simply to pull the plants and then to drain
the pond via the 2" cleanout in its base. Takes 10 minutes. I
ignored the muck last year, so it is several inches deep.

We have a flat pool cleaner head and a pool hose. I tried pulling the
plants and then using a net to grab the larger junk from the bottom of
the pond. After that I tried using the head to 'sweep' the floor of
the pond. It did a great job of grabbing the muck. The end of the
pool hose alone pulls only from a small area. The flat pool tool
pulls from all its edges and cleans a strip at a time. We had to let
the muck re-settle a couple of times, by we were able to pull
virtually all the much fdrom the pond without fully draining it and
losing the small ones.

Jim