Question
I live in Richmond, VA and this spring installed a 2000 gal, 3-ft deep pond with about 15 koi and goldfish. I've read both positive and negatir to remove the pump. I've read conflicting advise regarding whether or not to run the pump throughout the winter. Can you please advise what is best for this area?

Answer
I live in central MD, Zone 6/7 which is colder than VA.  I keep my main waterfall going all winter with my OASE Nautilus 2600 gph pump.  I turn off my smaller pumped waterfalls and fountains.  It's been close a few times with ice forming on the waterfall but I've yet to have a disaster result (which would be water diverted outside of the pond or on top of the frozen pond).  

How is your pump and filter system set up?  If the tubing is buried, that will help keep the moving water warmer.  You also don't want a check valve because, if the power goes out, you want the water to drain from the system so it doesn't freeze and crack the pipes.  You also have the option of just having the pump discharge right there and not go to the filter system.  This would allow for some water movement and help to keep a hole in the ice if it moves the surface.

My page on winterizing ponds which includes a list of pros and cons to keeping the pump going is at http://www.fishpondinfo.com/winter.htm
If you read through my pond newsletters for the months of February (which covers January events) and March (Feb. events), you can read about how I keep the waterfall going.  I've used hot water and a sledge hammer as well as my hands.  I keep a de-icer at the top of the waterfall in my biofilter to help keep water flowing.  If you decide to not run the waterfall, I suggest running at least an air stone in the pond then to keep oxygen levels up.  This is all on top of keeping a hole in the ice for gas exchange.

Good luck!