Heck, you live in the middle of a bunch of desert rock formations.
There are ample models of naturl rock formations to chose from.

Most dense desert wood is excellent for aquariums, soak well, do regular large water changes, they work.

Plenty at the higher elevations in the mountains there as well as other harder dense woods.

Stay away from Cresote bushes(Larrea) obviously

Regards,
Tom Barr