congratts on the bio cube. It does look good, but you will most definately change your rock around.
I have a 12 gal aquapod. I kept my sponge in the chamber, but I cut some off the top and put a bag of purigen on top of the sponge. The intake screen is high so my water comes in the screen, over the purigen and through the sponge. It works pretty good.
I put a heater in the second chamber and upgraded my pump to the maxi jet 900.
I just ordered the 6 gal. bio cube!! I'm soo excited!
watch out this hobby is adicting!