I came home from work today and noticed a few pinkish-red blotches on the protein skimmer air stone, which is made of wood.  I’m inquiring over at ReefLounge.com to try and find out what it is.  So far I have one reply from a person who says it could be bacteria, considering the air stone is very porous and in an oxygen-rich environment.  I’ll edit this post as I find out more… if I find out more!