I've never tried sani chips either, but I love the aspen I use. I change it also about every 2 months or so, spot clean when it is messed on. I feed all my snakes in their cages... i just put an 8x11.5 piece of computer printer paper in the cage and put the thawed rat on the paper.
Here's what most people won't admit to. Aspen is digestible in small amounts. Sani chips are not. Think of it this way. A snake kills a rat in the wild. There will be leaves twigs etc all around. He's not gonna drag the rat out to a big rock and make sre its completely clean before eating it. Therefore in the wild they will have to ingest some amount of twigs or whatever. You just don't want to get TOO MUCH in there. THAT will cause an impaction.
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Chondros and colubrids... my 2 favorite types of snakes!
"Life is hard. Life is harder if you're stupid." - John Wayne