If your pond slopes to the drain, you can let the muck be pulled into
it and the filtered in your filter or allow it to settle in a vortex
or veggie filter. Ours slopes gently (very...less than 1/4" over an
8' radius). The fish stir the muck and the pump at the deepest part
pulls the muck out into our berm veggie filter ponds. It settles
there. We drain the berm pond annually, runnig the muck our a bottom
drain.

Jim