cyno or something else... ID?

[JasonWong]

Hi guys, can you please help me identify this stuff, cyno or algae or something else? I quickly go through the articles here but found nothing.
This stuff stick to rocks and is very hard to remove. Feels like plush.

 

[TheEngineer]

Can you take a less blue picture? Your description sounds like cyano. Are there bubbles under the mat and is it purplish-red?

 

[JasonWong]

Can you take a less blue picture? Your description sounds like cyano. Are there bubbles under the mat and is it purplish-red?

OK later. There are no bubbles and it's purplish-red.