Anyone have any experience with vivarium substrate setups? I'm planning a new project and was curious about charcoal layers. I plan to add one above the "aquifer" layer to help filter the water. There is charcoal sold for this purpose, but I was curious what/if any the difference between the charcoal sold for vivarium use and all natural wood charcoal for cooking is. From what I can tell they are the same thing just ground up into smaller pieces. Where my confusion come in is you can buy all natural cooking charcoal that is made out of different woods. I'm unsure if there could be issues with prolonged exposure to different style of charcoals. If anyone has any info or could post me some links on the subject that would be great. Thanks.