Repotting oncidium with lava rock

[Mercurianmad]

Hi guys! I’m going to be repotted my wrinkled oncidium and I want to ask you if I should use just lava rocks or a mixture of 40 percent lava rock, 10 percent perlite, 20 percent sphagnum moss and 30 percent bark chips?

I know once I repot the orchid I’m going to have to toss one of the pseudobulbs, as it is squishy and getting yellow green...no idea what the roots are like but as I said the bulbs are wrinkled.

Help is appreciated.

---------- Post added at 11:02 AM ---------- Previous post was at 10:58 AM ----------

Also is lava rock good for moth orchids?