I have a neglected-until-after-finals-and-job-interviews 10 gallon that is great (cherry shrimp, scarlet badis, few otocinclus) that has a nice solid carpet of hair algae on top of a dense carpet of glosso. I recently tossed in some frogbit from my 29G, and it seems to be doing well. However, there are recently tiny bits of red things (worms? don't appear to be moving. hair algae?) on the glass, and on bits of the hair algae... actually, they look like mini hair algae. and the hair algae itself appears to be partially turning red.
What is this stuff? Is it dangerous?