What is this???

[Ziggy953]

This has been on this rock for sometime now it was rather small when I got the rock about 4 months ago but it has started growing. It's very coarse, and hard I thought it was some kind of seaweed or something but now I'm thnking its a type of coral. Anybody have any ideas??

 

[roka64]

I believe it is a type of Codium. I have it in my tank and it appeared after an outbreak of hair algae. It seems they competed for the same nutrience and the Codium won out.
It is green right?
Did you recently have hair algae (just curious if my assumption on the outcompeteing is true)?

Click on my gallery, I think it is about the 5th picture.

 

[Ziggy953]

No it's not green and it was on the rock when I got it. It has just recently decided to grow. It is a slate blue/purple in color.

 

[roka64]

Hmmm, in that case, I am not sure if it is. I don't know if Codium is that color, most of what I have seen is green.

 

[Ziggy953]

I looked up codium and it doesn't look like that. I have no idea what this stuff is. It's really neat looking and is only in 2 places in the tank. The photo I posted and on the back of a much larger rock that I can't photo unless I have the PHs off and the lightbox off the tank and am standing on a ladder looking down. Im going to have to take all the rock and coral out of my tank in a couple of weeks to get 2 problem fish out and move the tank. I'll be sure to take pics of this stuff close up.