I've read somewhere in the past that too large an air pump will cause the w/f recirc. setup to not recirc....

I went with Xtra Crispi's idea for gettin' them to recirc. and like it that way better, cuz I can just close the valves on the res and pump everything in the system back to the res for testing or res changes...

When I'm ready to gettin it recircin' again just open the valves and gravity fills the system, simplicity