Please don't use the cat collar. I rescued a female ball python a while back and she was owned by a lady. The snake had mites and was told by the petstore that she could use flea powder in the substrate. When I got the snake it had problems galore. Irritated respritory tract, and severe neurolgical damage just to name two. I know that flea powder is bad and that the collars have the same ingredients imbeded in the plastic but the plastic will eventually break down with all the humidity and seep into the substrate as it dries.

If you are worried about the mulch having bugs you can maybe bake it for a bit to kill any thing off. 300* for 20 minutes does wonders just monitor it closely.

If you want to get rid of mites use provent-a-mite or similar.

You can also clean your tank with water and bleach solution but be sure to dry it and let it air out for a while.