When I've used aspen it's been shredded aspen from fleet farm, it worked out pretty well. I remember one time though, it was winter and as usual I was having trouble with humidity. I wet the aspen down real well and it seemed to work out well for humidity, but within a couple weeks I had mushrooms growing in my tubs. :O:O:O
I generally use newsprint but recently I ordered some bogus paper from uline that I'm going to try out.