Mag 12 - rated @ 1200 gph
@ 2 ft head - 1150 gph
@ 4 ft head 1100 gph
@6 ft head 910 gph
Lots of flow rates on this link: http://www.aquatictech.com/pumps.htmlMag Drive #2 Flow (gph) 250 7' 24 Flow rate on a 1 1/2" drain?...not sure, supposedly 1" is 600gph.
Is the tank RR or are you using an OFB?