I'm in the process of planning out my 29 gal. reef tank. My question
relates to the deep sand bed. I know that the deep bed denitrifies
better because there are anaerobic areas where bacteria can break
nitrates down. I'm wondering if one could "simulate" the effect of a
deep sand bed with a shallow(er) bed by putting a semi-permiable
barrier over the lower bed, and then putting more live sand on top of
that.

I was thinking of putting down an inch of live sand, then my
undergravel filter plate, and then another inch or two of sand. I'm
trying to avoid having 5-6 inches of live sand in my tank.

Thanks,
Juan