Green & white spongey-looking ball with sticky arms...

A fragment of yellow polyps I got a while back has something living on it that is spongey-looking in appearance, pastel green and white (usually greener than the photo conveys, and has little arm-like things that it sticks onto things nearby it. This is not its original placement and it sometimes has arms stuck to the glass, so it apparently sticks to whatever it seems to fancy to keep it stable. The open brain coral above it doesn't normally flatten out like that, and about a half hour after I took the picture the brain was full and fat again -- so I don't think that it's damaging the brain.

It is somewhat spherical with a diameter about that of a penny.

 

My guess would be a sponge. Should be harmless.

 

yea i have one too... just always assumed it was a sponge

 

pineapple sponge maybe?

 

Oh God no! Not the green and white sponge looking thing!

 

That gave me a good laugh. ;D

If it's just a common sponge of some sort, I'm disappointed. The child inside of me was hoping it was some super-rare extinct-outside-of-captivity coral from Palau or Atlantis or something.