I just noticed this thing growing out of a hole in my live rock a month or so ago. In that time it's gone from barely noticable, to about the size of my thumbnail. It's only semi-rigid as it moves a little in the current. I have no idea what it could be. Any thoughts?

http://i42.photobucket.com/albums/e332/pearsonhurst/HPIM3026.jpg

Looks to be Padina sp., you can see pics of various macros including Padina sp. in this Macroalgae slideshow (http://reefkeeping.com/issues/2006-09/reefslides/index.php). You'll see some can be very colorful and others drab and brown. Still it would be considered by most to be a desireable macro to have. It is calcearous and can put a strain on Ca if there's alot of it.

Cool, thanks. Never occoured to me it might be macro, but it does make sense if it's calcerous, as it popped up after I started dosing with kalc.