Rack substrate options

I used to house all my snakes in separate bins scattered round my room. I used astro turf for a while but it got difficult to see when they peed on it. It was black turf. Then I switched to paper towels for the whiteness of them and the cheapness. They are working ok but I'm having a bit of a problem keeping humidity up in the bins. I have a rack system set up with 28 quart sterilite bins and back heat. I'm wondering if switching to cypress mulch will help hold humidity better than the paper. Or if any of you guys have other solutions I would be happy to take them into consideration as well. For right now I have been misting every other day or so which I'd fine but gets annoying after a while. If this is the only solution then I will have to live with it but I'm open to ideas. Thanks guys.

Cypress will help keep humidity up. I was having a humidity issue and then realized I had too many holes in the tubs. Covered up some of the holes and the humidity is much better now. I use paper towels. And just move the water dish over the hotspot when they are in shed to raise the humidity.

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I use a mixture of cypress and reptibark. It works out well for me :)