I'm relatively new to orchid growing, about a year and a half into my
madness, but I haven't yet heard much discussion about fungi of various
sorts inhabiting the growing medium and what, if anything, one should do
about it.

For instance, I've noticed various tiny mushroom-like fruiting structures
which I don't worry too much about. But lately, in my Angraecum
sesquipedale, I observed a rather vigorous white mycelial mat or fan
spreading throughout the bark-based medium. My thought was: How good can
this be for the longevity of the medium, not to mention the health of the
plant? So I soaked the pot in a Physan 20 solution (1 TBSP/gallon), watered
it a little less and thought I had licked the problem. A couple of weeks
went by and one morning I saw growing out of the bottom drainage hole of the
suspended pot this huge white gilled mushroom with a cap about 3-4 inches in
diameter!

Is this cause for concern, or do orchids and orchid growers just live and
let live?

Jeff