What is growing in my tank? Pics added

[tim the toolman]

For some time now i have had these thin stony sticks growing in mostly the unlit areas of my tank. They are starting to spread quite heavily and my questions are, A. Should I be concerned and B. What can I do to get rid of them. They are not tubes, but occasionally when I do a heavy feeding I will see them slime a bit. I will try and post pics asap.