Sand is a no-no for Igs for a start. They do lots of tongue flicking for chemical cues and risk ingesting substrate so anything loose needs serious consideration. Whenever I have had Igs in my care I have always used linoleum as a substrate simply because it's easy to clean and can't get ingested. Ig's being herbivores make a lot of mess when they defecate so any substrate with absorbent qualities is going to soak up urate and harbour bacteria.