A cymbid mix includes bark, but using the bulk stuff like you use on your garden usually comes with bugs. A good mix includes some sand, bark, perlite and peat moss. You can throw a handful or two of plain old dirt and some time release food also. It must be a very open humousy mix...think of the junk at the edge of a pond or underneath the trees in a woods. The top layer is made of decaying bark, some dirt, some mossy stuff, leaves, etc. Try to replicate that sort of thing in your mix.