Clear Bubble formations on Rockwork

[Jay]

Once again I know its tough without a picture but what I am experiencing is small colonies of tiny little clear bubbles all throughout my rockwork, does not look like any kind of algae rather just tiny little air bubbles. Im just wondering what it may be and if it is harmful to my tank. Does anyone have an idea of what I am talking about or am I being to vague?:dontknow:

 

[nahtanoj]

my guess would be some red algae. it doesn't grow much but it puts out nitrogen bubbles like crazy, i had it a few months ago, just started feeding less and it went away.