Loose substrate will cause impaction

Ask around and someone will tell you that loose substrate is a gamble, that your animal will swallow it and end up blocked. It is one of the most repeated warnings in the hobby, and it keeps a lot of enclosures looking like a hospital tray.

The picture is more complicated than that. No substrate is completely without risk, but impaction is very rarely caused by the bedding on its own. Animals kept at the right temperatures, properly hydrated, and fed appropriately sized prey almost never run into it. Animals kept too cool cannot digest properly. Animals kept too dry get dehydrated. Those are the conditions that turn a mouthful of substrate into a problem.

With that being said, very young animals under three months are better started on paper towel. Fine sand is not suitable for juveniles of most species. And every species has its own answer, which is why our care guides name the substrates we recommend for each one rather than giving a single rule for everything. There are real exceptions and they are worth respecting.

For many species the greater risk is the opposite of what people worry about. Keeping a humidity-loving animal on bare tile because loose substrate feels dangerous causes dehydration and shedding problems that are far more common than impaction ever is.