I haven't nailed down a substrate yet, still on paper towel. I get a little obsessive when it comes to certain things, so the routine I find myself in now is I get home from work first thing through the door in the morning or first thing when I wake on days off, and I change out the paper towels, wash down the fake plants, and change the water. Don't know if this is too often, but I figure you can never be too clean, and I have to get in there everyday to give fresh water anyway.