What do you keep them in?
I have a 10 gallon tank, and when I get a new shipment of crix, I line it with paper towels with masking tape to keep it in place. Every other day, I gather all of the waste, dead crix, and shells and scoop it out. I also throw out any old food, and throw out the water crystals, dry or not. I replace the food (I use beardie pellets and greens) and water crystals.
When I have a lot of crix, sometimes I do this every day. It's imperative to remove dead ones, as the dead ones will kill your lives ones.
I also use the egg crates that come with my orders. I usually order phoenix worms, too; they send them in a separate box and use egg crates to secure my packages, so I always have spares. If I need extra 'furniture' or hide spots, I use toilet paper and paper towel tubes. Just throw them out when they are too soiled. Usually every order of 500 crix is about time for them to go.