Growth under my favites?

[Kevin207]

I noticed this growth under the part of my favites coral that suspended in open water like a coral shelf.

Could it be two sponges growing there? Will they harm the favites coral growing on the top side?

 

[Kevin207]

Here is a view of the favites coral as you look at it from the front of the tank. It doesn't show the growth as well, but puts things in perspective.

 

[SnowManSnow]

those are sponges. they wont really hurt anything, just don't let them encroach on your coral tissue. if they do, just scrape them off with a plastic knife or somthing. no biggie

One unconfirmed thing that I would check though... seems everytime i get these things growing in my tank somthing is going on with excessive nutrients in the water, you may want to check the nitrate / nitrites a few times just to make sure everything is cool. I don't know that the arrival of these things has anything to do with this... just somthing ive noticed on my tanks.

b