When I used aspen (we use newspaper now) I'd clean the solid urate or poop out and take all the aspen down to the bottom of the tub plus a few inches around the mess just to make sure it was totally clean. I'd regularily finger fluff the aspen to give it back some loft it loses from the body weight of the snake plus I could then feel if any was damp or clumped. Once a month to every 6 weeks everything came out down to the bare tub so it could be properly cleaned and all the substrate replaced. Hope that helps.