return pump size?

[fmelindy]

based on my own experience with quiet one pumps (I've owned almost all of them), I'd be more inclined to go with an eheim. Quieter, more reliable, always restarts after power out (unlike the quiet ones), and maintains better flow through plumbing. Just my .02. Every quiet one pump I've ever owned, I regretted buying in the end.

Oh, and I think putting that much flow through your 20 gallon sump is only going to give you micro bubble problems. At least that's what it did for me! Now I'm using an eheim 1260 (635 gph) in an approximately 40 gallon sump.