sounds good but i just realized something while looking at the stats on the pumps.
mag
12---18---24 at 5' head (about what i have.)
1120 1200 1850
power
12--- 18---24
110w 145w 265w
if i add a 12 to the 18 i have i will get
2320 gph @ 255w
and
a mag 24 will give
1850 gph @ 265w
so pretty much same power and more flow. with the option of borrowing a pump if i needed to. or taking it off if my load changed.
stats from here
http://www.marinedepot.com/ps_AquariumPage~PageAlias~powerheads_pumps_danner_mag_drive_supreme.html
This would just work so much better for me.
assuming i can find a 12 now.