you could put heaters in the intake, and/or skimmer sections too, as well as the sand bed section. the return section is the only place i wouldn't keep heaters due to it's constant fluctuation. also, you may get some microbubbles from the water toppling over the partition between the sand bed and the return area, depending on the gph
going over there.
i would also put the skimmer in the intake section, not after the live rock. the reason is, i don't want to skim that water and the pods
out of it. i would want the pods
to have only 1 pump they'd have to get through in order to make it back to the display.