Change subtrate

So, I just got my first ball python and at the moment I have some kind of brown bark as subtrate. I noticed that it was kinda expensive, and alot of people say that aspen will do just fine aswell. Is it okay to change substrate? My ball python have always had the bark substrate before so I guess he is kinda used to it. He is still a little baby though.

Yes you can change substrate. If the aspen does not work out you could always mix the current substrate you have with the aspen. A lot of folks use cypress mulch because it holds humidity very well.