What’s on my rock?

[kinder23]

Can anyone identify these spots. Doesn’t looks like pictures from any nuisance algae guide I’ve seen. Had some Cyanobacteria in my fuge and some of these spots in my DT. I killed the light in my fuge for a few days to kill it and now these spots have increased in my DT. Seems different from cyano as it can’t be blown or scraped off rock easily.

 

[aresangel]

Could it be a dark red coraline? I have that it doesn’t blow off but is softer feeling. Almost slim like.

 

[1spotpooalot]

Had something similar a while back. In a mature tank. Wasn't an issue for me

 

[thespsguy]

It does looks like coraline, which is good

 

[kinder23]

Thanks all!