Dark brown/green algae…what is this crap?!

[Necrodaemus]

This stuff has been growing on my rocks for a while and I cannot figure out what it is or how to get rid of it, short of pulling everything, bleaching and starting over, which just isn’t an option to me. Cyano is not the answer….it encrusts similar to coralline but does not have a calcium base. It is very hard to scrub off….plastic bristle brushes do almost nothing to it and nothing eats it.

 

[Gman83]

I've seen some similar pictures posted before, I belive others said a type of sponge

 

[Gman83]

Sorry, I'm not much help

 

[Necrodaemus]

I've seen some similar pictures posted before, I belive others said a type of sponge

That very well could be a possibility. My silicates are high as I don’t run a silicate buster cart on my RODI and ICP came back showing that as the only thing in the RODI test.