What is this ?

[peterthegamer]

Seems like a sponge but has spread to other rocks too. Thank you in advance.

 

[dwest]

Seems like a sponge but has spread to other rocks too. Thank you in advance.

Looks like a sponge to me.

 

[Rjukan]

Looks like a sponge to me.

Same here. Nice color!

 

[peterthegamer]

Just never expected sponge to spreading like that

 

[mtraylor]

Looks good. That is good thing.

 

[Coralreefer1]

That is basically your standard sponge that, often times, comes in as a hitch hiker on coral or live rock. It comes in many colors from purple to pink to yellow and blue. They are filter feeders and good for a reef tank as along as they don’t encroach and impede your coral growth and polyp extension.