Moisture Vs Humidity

[BugsSnow&Milly]

Hi!
My 3 purples and I have moved from a much colder climate, requiring heat pads and 3x daily tank sprays, to not needing extra heat and natural humidity at about 80%. My question is: the substrate is very dry although the air humidity is not. I want to make sure the substrate (mix of play sand and coco fiber) is sufficient for them to molt and build tunnels in if necessary. They have salt and fresh water bowls. If I spray the tank, the humidity will be too high.
Secondly, I want to replace the substrate as it’s been a couple years and my crabs seem to hate the addition of sand vs just coco fiber. I am not sure if coco bricks would be a good idea since it has to soak in water. Any comments are appreciated!

[curlysister]

It is important that the substrate is moist enough to hold it's shape, no matter what you use for sub. If it is dry, you will need to add water to it - instead of misting, you can just pour a little along the edges. There is no such thing as 'too high' of humidity. So it doesn't matter if it is higher than 80% in the tank when you wet the substrate.

[BugsSnow&Milly]

Thank you so much for the information!!

[Jlmills525]

you can add "leaf litter" to the top of the sub to hold the moisture in as well (bonus, they can forage on that too)

[BugsSnow&Milly]

Thanks for all the input!
I’ve always managed to keep air humidity up but never knew to keep substrate wet enough to dig. Once I began doing so, my crabs have been so active! I’m not sure how to keep doing this with a molter, if wetting the substrate will disrupt tunnels or not?
Either way, I’m happy for the advice and so are my crabs! It’s awesome how I keep learning after 6 years of having my hermies.