Even though Paphs need a lot of water, their roots also need oxygen to thrive and grow. This means that Paphs should be planted in a mix that retains water but which also drains well. When the medium breaks down over time, it can hold too much water and smother the roots. Therefore, Paphs benefit from annual repotting.
I like to use small fir bark or Orchiata, mixed with a small part perlite and charcoal (about an 8-1-1 ratio). The mix should always be a little moist, never bone dry. I typically water twice a week, but if you aren’t able to water as frequently, adding one part Sphagnum moss in the mix can help retain moisture between waterings. I sometimes also top-dress with Sphagnum.
Which Pot to Use
Paphs are typically grown in plastic pots, to better retain moisture in the mix. The pot should be about an inch larger than the existing root mass, with the base of the plant just at the level of the top of the pot. It is OK to re-use the pot if the roots have not overgrown it. If re-using a pot from a different plant, be sure to sterilize the pot with a 10% bleach solution before using it again.
When it is time to repot, start by washing your hands if you have handled any other plants. Gently tap the plant out of the pot, and try not to break any roots. Using a sterile tool (bleached or flame sterilized), cut off any dark brown, mushy roots. Healthy roots should be plump and light brown, ideally with a white growing tip. At this point you can also gently peel off any yellow or brown older leaves from the plant. If the plant has divided itself, you can plant into two pots, but keep in mind that Paphs typically do not like to be manually divided—cutting the rhizome can lead to bacterial infection. If your plant has lost most of its roots, putting it into a smaller pot will help it re-grow new roots (this can take 3-6 months).
Discard the old medium, and gently but firmly repot, with the media packed tightly. Keep the new medium moist, but don’t overwater at first. This will help the plant put out new roots. Good luck!
Ken Mettler also added:
I have very soft water, and many Paphs like calcium, so I have started adding oyster shell chicken grit (not the granite kind) to my potting mix. I use about 5% by volume. It's too early to tell how my plants will do, but this should mimic how many of them grow in the wild, with organic material on top of soft limestone.