same here as bob, mag 5 with +- 4ft head, however it runs my tidepool wide open, almost a little too much. If you get a wet dry that can handle a higher GPH, i would go with a step or to up from the mag 5
I have a Little Giant 3-MDQ-SC [does 630 gph at 4' head] on my 58g. It's an external, I like it as it handles additional plumbing well.
On my 40 I run a Mag7 thru a scwd, does ok too.
I'm thinking of a Mag 9.5. I want to put it in the sump and run PVC out of the sump and T it off at the bottom back of the tank. Then run it up to the back two corners for the outlets. Will the Mag 9.5 be too much flow? What do you think?