Hello! I want to start off by saying all substrate experiments are happening in a rack with no animals living in it.

I have been experimenting with DIY substrate ratios. My animals are currently pretty happy on newspaper in their other racks but a substrate blend really appeals to me and I'd love them to be able to root around. The closest I have gotten so far is my latest mix of 50% topsoil and 50% peat moss in a fairly thin layer (1/2" or so) there is no water bowl in the experiment tub yet but it is heated and the humidity has been around 80%. I'd like to get it down a smidge under 60% and a slightly thicker substrate layer ideally.

I really want to avoid drilling holes in the tubs themselves. The rack is from ARS and there are ventilation holes in the shelf panels already. The humidity of the room roughly a foot away from the rack is 34% so I would prefer to avoid fans or dehumidifiers for the sake of myself and my other animals.

What can I add or change in my substrate blend to help?

I am trying to stick to materials I can source from my local garden/hardware stores and deep freeze to sanitize. There is only one pet store close to me and they have insane prices. I have tried ordering online but have bad shipping experiences. I know there are good pre-done blends out there but I'd really like to stick to DIY.

As an additional note, there is no store near me with cypress mulch that is not dyed so that is not an option.