Not sure from the pics, but might be blue green algae, which is actually a primitive bacteria rather than algae. I just got rid if it in my tank with a course of erithromycin. It isn't supposed to impact your biological filter, but my tank did go into a mini cycle afterward. Could have been from the dying algae, though. It's gone now, though. Anyway, I would google it and look at lots of pictures and try to compare it to what you are seeing.