I'm building a veggie filter and have a couple questions. I'm going to
have a 3" pipe near the surface of the main pond to gravity feed a
filter/box with the pump in it. The water will then be pumped up to the
VF and flow back into the main pond by gravity. My question is, the pump
I'm getting is 2800 GPH, and I'm not sure if that's too much since the
pump box will be gravity fed by only a 3" pipe at the surface.

Here's a few pics

http://members.cox.net/michaelshaffer/vp1.jpg
http://members.cox.net/michaelshaffer/vp2.jpg
http://members.cox.net/michaelshaffer/vp3.jpg