As you'll effectively be removing water along with any muck/silt, how comfortable are you with getting 'new' water into the pond?

I ask because you may not have seen the pond through cycles of summer without rain, or even some of the droughts we experienced over the past few years in Western PA.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."