I'm not great with Phals..I love them but I'm not very good with them.
Each time I get a new phal there is a healthy amount of air roots and then after a while, there aren't any..they shrivel up and dry out....the plants keep growing (and sometimes even bloom! ) but they never grow anymore air roots...what am I doing wrong?
The aerials on many of my phals will dry up also .. being the air humidity is extremely low .. what I do is place sphag moss on the top of the medium for the roots to hid in and mist them to maintain moisture - it also help to give a little humidity to the orchid - .
It's working for mine.. but I don't advise it for everyone ..
Two of my phals have lots of air roots, and i try to keep up the humdity by using moss in the bottom of the outer pot, and i mist only the air roots more often than i water the hole plant (mist about two,three times a week in the summer).