say IF i were to have some rye substrate in need of a casing PH balanced pete moss is ideal, but how do you balance the pete moss, do you ph balance the water then mix it with pete?
use jiffy mix, not the one with perilite unless you have some vermiculite to add, it is already ph buffered.
If you cant get jiffy mix make your own, 50/50 verm and peat with a pinch of hydrated lime for ph ...
or in an emergency you can use very little straight verm...its the worse choice but will work just get it on even and thin, a casing layer is not a must it just helps maintain 100 humidity where hyphal knots and primordia form but still allows o2 to penetrate...
also 50/50 coco coir and verm works, also with a pinch of lime, but your casing layer ideally shouldnt have ANY nutes and contrary to popular belief Coir has almost as much as Horse poo but it still works as long as you dont allow it to colonize the coir and cause overlay, icky myc growing ontop of myc...it just kills the spot.
if you must use coir wait until you see hyphal knots and or pinheads then "late case" it after that point comes...
hope this works good luck
if you must check your water PH do so and adjust first...to about neutral or a little alkaline around 8, adding peat will bring this down a little and then a pinch of hydrated lime will finish it around 6-7, thats fine... mushies like it around 6 too, give or take a little... but as they grow they make more acid so if you start too low it will be to acidic by your 2nd or 3rd flush...starting even at 8-9 is ok just not the best....