At least you know one of the parent is charlesworthii, and the other is a "maudiae type" which is a whole history of its own. lol
Phals seem to grow crazy roots whatever I do with them. Sometimes I just cut them off when they get all over the place and so annoying.
My paphs are in three different type of mix, well, actually four, but two of them are very similar. Straight sphag, straight bark (I believe orchiata) and a variation of this, and coconut husk chips mixed with hydroton, perlite, charcoal.
Of these, the last one gives me the best results with roots. so now I plant to pot up all my paphs to that mix. I've trid bark instead of chc, and the result was similar except I had to water more often with bark drying out faster than chc.
What do you mean by aquarium bark??