newbie piping questions - what size return - what size overflow?

[MikeInToronto]

Gave up on that "how much flow through my sump" thread eh?

I can only give you my opinions on your overflow. You'll need to choose your pipe sizes based on the size of your return pump. If your overflow can handle 600 gph you'll need the appropriately sized overflow pipe (as a minimum). Here's a calculator:
http://www.aquariumpros.ca/modules/O...ator/index.php

If you tell us the pump you plan to use, someone can probably give you exact pipe sizes for both.

As an aside: You should consider the Beananimal (or even Herbie) overflow. You won't regret it.