they look like hydroids to me as well can you get a closer pic mike?
If they are on a short stalk with almost like a feather dusterish head they are probably hydroids... and you should get rid of them before they start to spread... they can break off and float around the tank until they find a new place to grow.
Thay may not have an effect on those zoo's but I have lsot most of an SPS colony to them
But see if you can get another pic
This was the best image I could find by googling hydroids
http://images.google.ca/imgres?imgur...l%3Den%26lr%3D
HTH
Dan