Just another idea, and not sure it will work for your situation but on my
website click on *My Filter* scroll down and you'll see several "flower
pot" filters, this gets the filter out of the pond, so easier to clean, and
all the muck doesn't go back into the pond when you lift it out.
www.jjspond.us

Pump would still be in the pond but you encase it in empty mesh baskets,
similar to this: http://users.owt.com/jjspond/koipond/photos/set1/09.jpg
~ jan

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(Do you know where your water quality is?)