I use the following formula for phrags
1 part pumice
1 part commercial acid mix
1 part aspen fiber (used for pet rodents)
1 part peat moss
Worked great but has a short life span about 2 years
Am trying a new mix using:
1 part the old mix
2 parts granitic gravel
2 parts cypress mulch

And I use net pots!! I tend to overwater and I do spray almost everyday, unless it is dreary and cold like today was.