Switching to peat/coco substrate tips?

[JamesGSixx]

Salutations, friends! So I got a ball python and a red tail boa a month ago. My bp is housed in a wood glass enclosure, while my rtb is in a tub glass enclosure with paper towels as substrate. Their temperatures are spot on 90-95f on the hot side, 70-75f cold side. The humidity in both terrariums are pretty bad though ranging from 45% to 50%, this is when I don't mist. Both of them have humid hides filled with damp sphagnum moss to compensate but the problem is they're spending too much time on those hides instead of going to a regular hot/cold hide. Both snakes were being fed live mice before i got them. I fed live once, when i got them because i couldn't find any frozen rodents in my area. (philippines) then switched to frozen rats. weaned rats for the juvenile RTB and medium rats for the ball python. The BP eats like a champ and hasn't refused a meal ever since but the RTB has been refusing to eat after switching to frozen for about 4 weeks. I reckon it might be the humidity since it get's pretty low.

So I'm planning to change substrates to peat moss or coco fiber instead of paper towels. For the reason being so, I don't have to regularly mist to keep the optimum humidity levels up, and I could take out the big humidity box that's taking up so much space and so it looks better and naturalistic.

However, My main concerns are

• Mold - I keep a bunch of tarantulas and sometimes their substrate which is coco fiber/peat moss, seems to get mold. These don't really affect tarantulas though, so it's no problem for them, not unless it's been sitting there for a very long time. Note that these tarantula enclosures have more ventilation than the snake's tub/terrarium and it's already getting mold so what more with the vents that the snakes have?
• Mites - Again, a common problem I face with my tarantula's enclosures. When the substrate is damp, they usually start showing up, Not an alarming number but just a few that you can notice them. I'm not sure if it's the kind of mites that can be harmful to snakes but they're not harmful to the tarantulas I own. They look like tiny white round slow moving mites I think they might be called "hitchhiker mites".
• Heating - Where do I put the heat mat? should it be at the bottom of the substrate or should it be in the middle?

I also want to know about the maintenance of having those two choices of substrate. What are the do's and don'ts? What problems can I be faced with and how to avoid them? Thank you for taking up time to read this long post. Any advice or comments will be gladly appreciated!

ps I have Isopods and Springtails that I'll be using with the substrate.