After some experimenting I've found the best product for me is HAPI-GRO Cypress Mulch Blend. It's got no dyes and I've yet to see an insect in it. This product is made for landscaping, but is great as a substrate. Holds humidity well and is pleasing to the eye. You can't beat 3.48$ for 3 cubic feet. It comes in a bag that is over 30 lbs so you'll need a large plastic container (40gal +) to hold the excess. I bought my bag back in September I think, and I still haven't finished using it. I do full bedding changes about every 5 weeks in a 10 and 20 gal long so this stuff lasts a while.

Here's a link to the product

http://www.lowes.com/pd_92889-76450-...ductId=3467633