tye_c, do you use a solenoid and a float switch for your gravity fed auto-top off? If so, this sucker will work great for you. It will actually just sit inbetween your reservoir and your sump.
Buckeye, I can't be certian, but my assumption is this does not come with a autotop of switch, solenoid, or powerhead to turn it into an auto-top off device.