Rain Frog, I read that post on the epoxy background and really appreciate your help! That sounds like a great idea. I will let you know how it turns out (it will probably be after Christmas because that's when I'm getting the biocube
that's ok, because epoxy is best cured in warm temperatures...this is really not the best time of the year to try it. I advise you to mount some heat lamps over the curing epoxy in a shed to raise the temp at least to 120 degrees for four hours (or whatever the article says).
The vivarium mortar I've been told by Cindy herself is designed for small applications. You have to be careful not to make layers or anything too thin or it'll crack. So, not a good idea if you want to make a background.
However, for small rocks or something it'll probably work well. Just be careful with pH if this is for a fish tank.