Potting medium for mini phal

[MrHungx]

I was wondering what potting medium I should use for a mini phal. I generally use medium to coarse fir bark with charcoal and perlite, but this combination dries out rather unevenly in the small pots of the mini phals. Usually the top half dries within 1-2 days after watering and the bottom half is very moist. I never know when I should water it. The plant seems to suffer when I err on the dry side. I have currently switched to using hydration for my mini phal which should hopefully solve this issue for now.