Just upgraded from the Top Fin 30 to the AquaClear 70 for my 29 gallon today. I am loving it already as there is sooo much extra room. Here's my question, I know I put the mechanical filtration and the bottom, chemical in the middle, and biological on top. Where should I put crushed coral? I just kind of lumped it in with the chemical and put it in the middle. Also I might use a nitrate reducer at some point (if it becomes necessary which so far it seems okay without). Should that go in the middle as well?