Aw fer cripes sake dude. People with ponds don't need pond pumps cuz the pond takes care of itself. In other words, the natural forces that created the pond will take care of any pumping of the pond that may be required. You buy a pond pump when you ain't got a pond but think you should have a pond and by god you're going to have one. Next you dig a big giant hole and fill it with water. When all the water drains out you figure out you gotta put a liner in, so you do, and again fill it with water. Now the 'pond' becomes a stagnant pool of mucky gross slimy things, so you figure this would be a great place to have a pump so's you can pump out the stagnant slime and add fresh water as need be.

I think.

I've never actually pumped a pond okay? Sometimes when I'm willing to reveal my deepest fantasies I let on that I wish I had a pond that didn't need pumping, but even then I'd get a pond pump just to say "oh look at my groovy new pond pump - isn't it rather smashing?" to which all others would say "wtf you be needin a pond pump for when you aint got no pond worth pumpin?"

I think...

Pond pumps help to recirculate stagnant water (which are breeding grounds for mosquitos). You also need a pond pump if you have fish, because you will need to aerate the water. A pond pump is also a necessity if you want to have a waterfall, fountain, or spitter in your pond.