New to the forum, I've been quietly building up materials for a paludarium for a couple months, now. I was just wondering if the fluval volcanic soil stratum would also work for the substrate's drainage layer? They're slightly smaller than clay balls and I'm assuming the same material as the volcanic rock I've seen some use for drainage. I only ask because I have a lot left over from planting a new tank, and figured that if possible I could make use for it.