I have the Megaflow 125 and i've had no problems with overflows or floods at all when i shut off the pumps or the storms down here do it for me. It's a wonderful system.
I do have it draining into a 30gal rubble/tufa/base rock sump, and the main sump as well.
I also have my piping rigged so it can drain into a 3rd sump, when i'm ready for it.
Maybe, it's overkill, but it works for me.
i gues my point is, get the Megaflow, you won't regret it.
125gal. megaflow. Fish Residents:
Yellow Tang -(Junior), Flame Angel -(Flamey)
Bicolor Blenny -(Butch), Randall Jawfish -(Jaws)
Lawnmower Blenny -(Lenny), Talbot's Damsel -(Dottie), Tomato Clown -(Ketchup)
Nameless fish include, Neon Blenny, Singapore Shrimp Goby, Yellow Tail Damsel, 1 Skunk Cleaner Shrimps, purple pseudochromis.