Mobass, here's a link to a discussion on this subject, some people use rakes to stir up the sludge to release bottom gases, I do it from a canoe and punch the bottom with a kayak paddle, it doesn't seem to hurt the fish when the gas is released, but they probably scatter from that area with me poking around.
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=137648&fpart=1