Can anybody tell me is this fungus? on manzanita wood

[touchofsky]

I recently noticed little round brown balls on a piece of manzanita wood in my 10 gallon planted tank.  They are hollow inside.  They were slowly spreading on the wood, and today I scraped them off with the siphon hose and removed most of them from the tank.  I don't have a bristlenose in that tank since it is only 10 gallon and a bit small as a permanent home, but do have otos and Amano shrimp, although they don't touch these.  I was wondering if anyone has seen these before?  I do have a baby bristlenose I could put in for a while.  

Here is a picture.  Any ideas as to what these are would be appreciated.