You're going to get a lot of answers on this I expect. I use MSU -
http://www.aos.org/orchids/add... it works great for me and is readily available on-line though it's not cheap. I buy Phals from Walmart when they go on clearance and MSU has really brought them back to life. I use the RO (reverse osmosis) formula as I have a little table top system that I use to make it.
