I think I know this one. I think your tank is about the same age as mine (3-4 wks). While my tank is new the rock came from an established tank. The behavior closing up with the light sounds like what I have. I think it is an Orange Ball Anemone. Here is the link to my post http://delreefclub.org/index.php?option=com_smf&Itemid=28&topic=1231.15 IF it is they seem to be a good thing and are filter feeders. I have a few and they are all located in holes in the rock.
It was really hard to get a picture of it.
Hope this helps.
Not planning to doing anything to get rid of this. Now the hair algae on the other hand…
YahoO I was able to answer a question right. BTW the picture is from my tank and with help from everyone here was able to guess at orange ball anemone as it is the closest fit, especially the opening at night part.
gee and to think i was getting ready to try to kill it! i guess thats why we found 1 at petkare underneath of a rock its amazing how many things u find in a tank with a big predator that doesnt mess with corals ( a big blue cod grouper) we found 1 of those a couple of zoo’s ummm a colony of featherdusters and a few other things after we sold that guy
MiniMomma little tip HJack
When you crop with paint move the sides in it make a smaller pic. If the image is takes up the full area and you are unable to find the mark to pull in the side; click on any of the tools in the tool bar and you will be able to move in the sides. Sometimes when the image takes up the entire open area it appears like you cant bring in the blank area.
