I use repti-bark for my turtle. When it's dry it's probably the cleanest substrate I've used, but if it gets wet it takes maybe a day to get really gross. I wouldn't want to use it for any animal that had to have high humidity just because I think it wouldn't take very long to start breeding some nasty bacteria. Plus, I wouldn't use it for any animal that ate in its enclosure. It's probably the most fatal bedding to ingest IMO.