Here is a crazy idea, set the egg crate up on pvc pipe legs so 80% of the rocks don't even sit in the sand. Here is a link to the post where I wrote it up how I did it in my tank build:
https://www.reef2reef.com/threads/ron-reefmans-50g-cube.409412/#post-4867204
And here is a photo of the final result. Now remember, more than 80% of this rock is 1" or more above the sand. And there are several reasons why this worth doing.
P9020001 R1 by Ron Lindensmith, on Flickr
https://www.reef2reef.com/threads/ron-reefmans-50g-cube.409412/#post-4867204
And here is a photo of the final result. Now remember, more than 80% of this rock is 1" or more above the sand. And there are several reasons why this worth doing.
P9020001 R1 by Ron Lindensmith, on Flickr