I recently finished my tortoise and box turtle outdoor enclosures. I was careful not to use any that had perlite or vermiculite. Unfortunately I did not know about guano. I didn't even know what it was until now. I am wondering if this is a serious problem. Both enclosures have an inch or two of cypress mulch but the Russian of course likes to burrow so he will most likely come into contact with it. Any information is much appreciated. Pictures of the new enclosures will be coming midweek. Thanks