Potting Medium for Dendrobiums ?

[craigb6883]

Hi im fairly new to Orchids so still learning the basics and im ineed of a bit of help, I have 4 Dendrobiums Sak Da Beauty , Burana Pearl , Kim Long Pink and Airy White I have them on my windowsill at the minute and the pots I got them in are way too small as they are practically splitting so im going to repot them into a 9cm pot as there currently in 7cm ones I have taken them out and they all seem to be attached to a piece of bark so i was wondering what i shoud use for the potting medium ? should buy some bark ? or could i use sphagnum moss as i already have some from repotting some phals last week.

what would you recommend i use ?

many thanks
Craig