I'm following The Art of Keeping Snakes (along with some helpful tips from a few others) for creating a Bioactive Substrate System for my ball python. I know I will probably be able to answer my own question as time goes on--but if anyone has any experience with this, I have a water question:

I ended up using some "larger-ish" lava rocks in the rock/water layer----so the rock/water layer is pretty uneven (with dips and valleys as you look through the tank). Because it is so uneven I have some substrate significantly either above the water or slightly submerged in the water. I know I don't want any rotting--so too moist isn't good--but we also want decent humidity for the snake as well. I will definitely be using a different rock when we schedule a redo--however I don't want to take the whole tank apart to change out the rocks now if I don't need to. Any tips/suggestions welcome.

PS. We put the snake in his new Vivarium last night and he was a completely different snake!!! He LOVES it!!!