Live rock turning dark brown

[RTab619]

Assuming this is just diatoms? Haven't seen it this dark ever. Established tank

 

[KJ]

I hope this help.
A Simple Guide To Common Problematic Algae And The Means To Control It..

 

[KJ]

Look like turf algea sorry for my English.

 

[Reefing Madness]

No, doesn't look anything like diatoms. Have no idea what it is. Black sponge possibly?

 

[RTab619]

More pics... Rock is full of zoas so don't want to scrap it

Out of the water

 

[RTab619]

Thinking it's red slime now

 

[RTab619]

Don't think its Cyano anymore since I tried scrubbing it off with a toothbrush and I barely anything came off

 

[twilliard]

Eww for the algae but that is a gorgeous rock!

 

[RTab619]

Now I'm thinking it's really dark brown coraline. It's not coming off at all

 

[madtownguy]

I've never seen that, doesn't look like algae to me. Better hope it's not some kind of mutant coraline from outer space. Hopefully someone will know, I would not want that spreading in a tank.

 

[twilliard]

Slime algae?
peroxide it!