Sphagnum moss as potting medium.
 

I am not at all impressed with sphagnum moss as a potting medium for phalaenopsis. I have killed dozen because of the watering issue. I am going back to bark.:(

I can't use sphagnum moss for phals either. BUT, I can use it for cattleyas for some reason. With the catts I just use a thin layer over styrofoam, peanuts or LECA and that works well. And it looks like I also manage to keep paphs in sphagnum without anything else. But for phals is a death sentence, without exception.

I love spag! I use it for my phals that aren't mounted. I put it in the pot very loosely, I water and then I let the plant dry out completely, once completely dry I wait 3 days until I'll water again.

But you need to do what is best for your plants and environment! If spag doesn't work for you and bark does, I think that it's great you recognize this and change it! That's part of the fun about growing orchids!

I gave up on sphagnum also. It stayed way too wet, here in South Florida.

Sphagnum in plastic pots is deadly; in clay it's quite usable. Overwatering isn't the only issue with sphagnum - it gets very acidic very quickly, and with common fertilizers, it simply kills the roots with acid. You need to use tap or well water with it, or add calcium and magnesium to RO water. And let it dry out between waterings until it's crispy on top - sometimes 3-4 weeks between waterings.

I've used sphag in plastic pots ... I do use either an inverted net pot in the center, or some styro. - which I do regardless of clay or plastic pot, as well as for other types if media, but definitely a MUST for me in sphag.

Also a must when using sphag is to replace it at least annually.

I too don't really like sphagnum moss as potting media. But it has it's uses. One of the issues with regards to using sphagnum moss as a potting medium is that it stays too wet. That is true if it has been packed into the pot. If it is loose it dries rather quickly. As quickly as say bark or LECCA. Too acidic? Depends on which sphagnum moss you use. New Zealand moss doesn't get acidic for quite awhile if used loosely. So it is the way in which it is used that determines it's efficacy as a potting medium. I still don't use it much but here's is a catt that was just about to be thrown out into that dark abyss. C. Bow Bells which sat for a long time in bark, lava rock, charcoal/bark/sponge rock/peat moss and did nothing but get more shriveled with each passing season. Now it has thrown a new pbulb w/flower sheath and has numerous new buds growing. Hmmmmm. Oh and this moss is just laid in the pot without being pressed down into the pot. The catt is tied into the pot to keep it stable.

I too have had good success potting rootless orchids in small (usually clay) pots with sphag. Put styro in the center, taking up half the pot or so, tuck sphag around that.

I think most rooting hormones are acidic. Maybe there's a connection. Vedy interrresting.

I also use sphag, with a fair amount of styro in the center. Key thing for me is that I use SLOTTED plastic pots. In fact with the 3" slotted pots I have to watch out that I water them often enough, as those dry out pretty fast even in my high humidity terrarium. I also only use good quality New Zealand sphag.

Besgrow has a table on their site comparing the characteristics of NZ, Chilean and Chinese Sphag (although obviously they may be biased):

Spagmoss FAQ's