When using any rocks eggcrate is an amazing safety measure. When using rocks that could turn fall and crack the bottom of your tank its a worth while insurance policy. African Cichlids especially enjoy digging and moving their substrate around, when they do this they can cause they rocks to become unstable. If you already have an established tank, take the hour or so and cut the eggcrate, and lay it down.
Remember, its under the lighting section at Home Dumpster.
I actually found it in the dropped ceiling section (ceiling tiles) section at both lowes and home depot. I looked around the lighting section for 20mins and asked several employees who all looked really confused at the question. :lol: HTH