What is this black stuff on coralline algae

[krayzie]

Hi guys

I was wondering if anyone could tell me what this black stuff is on my coralline algae.

I have tried to remove it with a toothbrush but it does not come off and trying to scrape off with a finger nail it seems to be encrusted

My tank has been up for about 1.5 years and current parameters are
ALK. 8
CAL. 420
MAG 1400
Nitrate 10
PO4 0.08
SG 1.025
Temp 25c

Thanks

 

[Peace River]

Does it blow off or is it encrusted?

Here is a link to an R2R thread that may help:
https://www.reef2reef.com/threads/dark-red-coralline-algae.822948/

 

[krayzie]

Does it blow off or is it encrusted?

Here is a link to an R2R thread that may help:
https://www.reef2reef.com/threads/dark-red-coralline-algae.822948/

It does not blow off at all, scraping it doesn’t do much either

Would it be some sort of coralline algae?

 

[cloak]

I have the same stuff, (sort of) but mine is more of a dark burgundy. Just here and there...