Dirt or sand or a mixture of the two would be your best bet probably, not peat moss or planting mix. Planting mix in particular could be dangerous for multiple reasons. They generally have a warning on the bag for good reason. Also they contain fertilizers usually and chooks can and will spot and eat that... You don't want that. Artificial fertilizers can interfere with natural nutrition uptake. But perhaps you mean something other than the sort of planting mix I'm thinking of?
I use normal dirt combined with ash, or DE, or both, and lime since I put lime down everywhere they walk to control parasite eggs, fungi, pathogen burden etc. Regarding the 'what-ifs' with DE, not sure what you mean there, but it does seem there's a lot of useless DE available, I've had a useless batch or two myself, but also useful batches.
I used to use pool-filter grade DE until I ran out, so recommended that grade to others (as it was rough enough to work as it should, unlike some very soft DEs, and was not polluted or adulterated, unlike some DEs) but an American on this forum said "pool-filter DE contains lots of nasty chemicals" --- but the sort I bought didn't, it was pure DE with no additives. But I stopped suggesting that source of DE to people, you'd think they'd read the label but actually many of them don't, and it's also a good example of the vast differences between brands and countries. That's been a rather significant issue on all levels, whatever the topic, the difference between regions.
When I say 'lime' many people think I mean burnt lime or something harmful, so I usually specify 'the same sort that's sold for adding to livestock's feeds' and even then some people aren't sure what type that is, even though it'll be on the label... So I did a search and in my state what is labeled as feed-additive lime is the same label used for the next state for dangerously caustic, non-feedstuff lime... Argh, the incessant vagaries, lol!
Anyway, best wishes with your experimentation.
All advice most appreciated!
