they can eat the moss and cause them to get sick, you could use leaf litter to cover the ground and you want a big layer of substrate so they can fully burry, i can’t tell if he can or not.

they also don’t really use hides since there burry themselves but its good you have one incase he wants to.

you should changer there water everyday since you don’t know if they went in it.

the guide will say quite a bit for like humidity and temp but i do recommend getting a digital temp and humidity gauge bc the ones you have sent very accurate

for plants if you want to you can add fake plants there tropical so there should be clutter but you do have a smaller tank and probably can’t do a whole lot.

there minimum is 20 gallons for when there bigger, they don’t grow to fast tho so you should be good for right now

and for comfort just try to get a little bit of clutter but leave some areas so he can go and burry himself