Home depot is having a sale on red cypress mulch and I was wondering if it is suitable for substrate. Is the red dye dangerous? Would it be too coarse? If so I have an old food processor I could use to break it down a bit.

If there is a better cheap option please suggest. When I get my rack built (should be this weekend, heat tape gets in Monday hopefully) I think I am going to switch from packing / newspaper to some sort of mulch, but I am loathe to buy from one of the big box pet stores. I assume they are always over priced and I really don't like their husbandry practices.