When you say popping up all over, what period of time are you talking about, days, a week, month? Judging by the red tube worm at the bottom of the picture, they look to be about 1/4" - 1/2", is that about right?
I will try and get some better pics. They have started appearing within the last 4-5 months, and are spaced out throughout the tank. If they are hydroids is this something to be concerned about?