Substrates

[TortoisePepé]

I have currently been using a combination of both dried grass and hemp bedding for my little 1 year old hermanns, Pepé. After recently reading up on hemp bedding and the dangers, i decided to change my substrate.
I purchased the tortoise life (mix of soil, sand & limestone), and also purchased crushed oyster shell from the shelled warrior shop..
I received the tortoise life yesterday so gave it a go, an hour after putting the substrate into my torts table i went to check on him and he was not himself at all, his eye was covered in the substrate, i washed it from his eye, as i did this he was clearly in distress.. his eye became rather inflamed and puffy. After lots of tortoise cuddles he calmed himself down and today his eye is much better. I am now clearly too scared to use this again, but gave the oyster shell a go as im low on dried grass, He is now trying to eat the oyster shell, i know it is normal for torts to check out their new surroundings, however due to the rough edges, and after googling it, became aware that it was dangerous if the torts ate it and it also wore down the underneath of the shell causing infection. Again in a state of panick removed it, (im not very good with change). I am now wondering wether there is either a different reccomended substrate other than his dried grass and dried flowers, and wether i should use the oyster shell or is it best i dont?
Sorry for gigantic message..