What size would you recommend? Here is my setup: The pond is irregularly
oval, roughly 8' long and 4' wide (at it's widest) and about 3' deep. I
calculate it to be somewhere between 500 and 600 gallons. I've got a small
(~2 foot) waterfall at one of the "long" ends. I placed my pump at the end
opposite the waterfall to get better circulation, so the tubing ran about 6'
horizontally underwater and then up about 3 feet above the pond to the back
of the veggie filter, which spills back into the pond via the waterfall.

I tried out a 700gph PondMaster pump with this setup but got nothing more
than a trickle from the waterfall. Do I really need to go up to a 1500 or
2000 gph pump just to get a somewhat meaningful waterfall? By meaningful, I
mean about 8" wide, 1/4" deep.

As already mentioned, you need a bigger diameter pipe/hose coming from the
pump. I've got at least 1" hard pipe coming from the same pump, running on
13 feet of pipe with an 18" rise. It just pours out of a filter so affect
isn't a concern. For your waterfall I think you're going to need 1,000
gph.... and if you want to stay with the same brand go with the 1200 gph
Danner and minimum 1.5" pipe or tubing. ~ jan www.jjspond.us
-----------------

Also ponding troll free at:
http://groups.google.com/group/The-Freshwater-Aquarium