For hatchlings I like a 50/50 mix of fresh "Long Fiber Sphagnum".
(you Orchid people know what I mean) That choice is because I like how it looks.
&Cypress mulch. I use about 5" in there tank. I keep all hatchlings indoors for at least the first 6 months.
I find hatchlings love to "Dig in" & the 5" depth allows this without getting unduly wet.
I love the moisture holding quality of sphagnum but it can be very wet at the bottom.
I like the cypress mulch for support.
Hatchlings can dig in if they choose & if not they don't have to fight the sphagnum jungle while walking around.
This works for me because;
1) Its easy.
2) I'm lazy.
3) My hatchlings like it.
I will probably keep using this method until someone shows me another way that is better.
Remember that I said "I like it" & never said it was BETTER that any other method!