I can only get what I can get now.What you can do in your 90 to increase access to the substrate is put three base pillar rocks across the bottom and then bridge across those with larger base rocks so you have two caves underneath. Obviously the larger the caves the more access you have to the substrate. And then you could put your live rock on top of that. I used all base rock, no live rock, to keep the pests out. Of course, it’s all live rock now. Also, the three base pillars I cut flat on the bottoms so they would be stable.