Pump to tank size

[Delphinus]

Originally Posted by reef_raf

people shouldn't try to supply all their flow with a return pump. It seldoms does a good enough job, and they might be sacrificing other things (like skimming potential).

Just to add one more reason, the higher flow you have going up and down between tank and sump also runs the risk of introducing microbubbles. Not that this is showstopper to a tank but they can be annoying if they're really bad.