What do y'all pot Christmas cacti in?

[Fishkeeper]

What does everyone keep Christmas cacti and similar plants in? For that matter, does anyone grow them mounted?

I got a Christmas cactus last year. Not knowing that it was an epiphyte, I put it in regular cactus mix, although I kept it much wetter than usual cacti. Turns out, actual cactus soil isn't too bad for Christmas cacti, since it's well-drained. The plant's grown some, but has been a bit slow-growing so far, probably because it's not in optimal light.

I've repotted it into a much taller pot to allow for its starting to droop a bit, and I thought I'd try a custom mix. The goal is a reasonably nutritious soil with good moisture retention and excellent drainage, fitting for a plant that usually grows as an epiphyte. So, the ingredients are as follows:

2 large handfuls of the soil already in the pot, i.e. cactus soil.
2 large handfuls of a compost-based houseplant soil.
1 small handful of extra perlite.
1 large handful of thumb-sized fir bark chunks, chunk peat, and small bits of charcoal from my bag of orchid mix.

It appears to drain well so far. I'll test again when it settles a bit, and continue to check for moisture retention. If it compacts too much, I'll probably add more bark.