i had live sand in my tank for 8months and it was a fight with cyno forming on the sand it didn't breath well i found and now i have mixed he crushed coral with sand i have much better turn out lower phos,nitartes.
the water seems to flow better in the crushed coral (seems cleaners on the bottom) and i can notice more pods,bristle worms ,etc. to set up and find a home
and its about 5inches deep the whole way around the 135g