[wildfirejc]

In the past few months, I have noticed a new growth on my live rock of the nano tank.
It's blue-black and leathery.
Could anyone tell me what it is?

 

[deanp88]

Will it come off the rock if you blow water on it or is it attached to the rock?

 

[wildfirejc]

It isn't flaky - and won't come off the rock easily. It's thick and has a leathery to spongy nature. If you're thinking of red algae, I have seen this in my husband's tank and it is definitely different. It is also growing!

 

[Jadinop]

Black sponge. I'd remove it.