[TNguyen]

It pretty much depend on your style of scape. The way most people use ADA substrate is to have a gradual slope toward the back. For example, 1 inch in the front then slope toward the back to 3 inches. The depth is good for planting stem plants and such. This is for visual effect also. If you take picture from the front with a flat substrate, you not going to see the foreground much. Are you using any other plants?

I think Mike Senske have too much to drink when he did this.

http://www.aquaticplantcentral.com/...on-nash/58481-you-can-never-use-too-much.html