I have some in both. Although I think I like the sprag more then I like the bark. Bark gets funky sometimes. I'm slowly switching all my phals over to a combo of coconut husk and sprag.
I agree with the mix of bark and Spagnum as there is a combo of good drainage and moisture retention. I do think that whichever mix one chooses, the main difference is in how you water-ie pure bark=more often
I use sphagnum (brazilian), mixed with coconut chips and carcoal. If I have Chilean sphagnum, I use it pure with good draining material (clay pieces and carcoal). Phals don't like tree-fern fiber (my favourite medium).
I am switching over to a bark mix in a clear plastic pot with cuts in the side. I think it actually looks pretty good and I can easily see if they need watering. I like the ease of spag for water retention, but I am nervous of any rot going on. One time I waited until the spag was on the dry side and I (for some reason, don't ask) didn't even notice the leaves had started to look stressed. Regards, Mary
I'm currently trying out Semi Hydro, Bark, and Sphag. I have to say that S/H and Sphag are the easiest to water, but Sphag seems less troublesome that S/H. Not sure yet. However Bark seems healthier for them, better humidity/ventilation mix.
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"We must not look at goblin men,
We must not buy their fruits:
Who knows upon what soil they fed
Their hungry thirsty roots?"