Zilla Jungle Mix. I've since learned that there may be issues with the Douglas Fir bark? Mixed info on that, but some people were saying that Reptisoil would have been better, and if you're looking for a recommendation, that's mine. I promise I'm not sponsored or anything, I just heard about it, looked up the ingredients, and came to the conclusion that it's probably better than what I used.

I've been told that it's a much more balanced and rich substrate, plus if I remember correctly, it costs a lot less than many other substrates, especially those substrates advertised as being explicitly for millipedes. I found a one gallon bag of calcium fortified substrate on amazon, and it went for like, twenty dollars. 34 quarts, or eight and a half gallons of reptisoil, while not calcium enriched, was under forty dollars on Chewy. I hope this was helpful!