Please I.D. this for me

[kinerson]

I have been dealing with this stuff for many months. I would describe as a slippery snot clump when removed from the water. In the water it reminds me of cotton like you get in a container of medicine. It seems to want to hold together and when grown in enough I can gently remove sections of it if I'm careful although there is always stuff left behind that regrows. If its not grown in heavy then removal is harder. Lots of air bubbles form in this stuff. Its color varies from light brown to dark brown. I think it gets light when its stressed. I don't know if its bacterial or algae. I have tried a cyano treatment as well as turning off the lights fora few days. It seems to get lighter in color which I took as a good sign but it isn't enough. What is this stuff???

 

[kinerson]

Here it is growing on a sidewall of a fiberglass frag tank…
The wall was scrapped with a putty knife just 2 weeks ago. I should also mention it doesn't seem to want to grow on the sand bed. It focuses on hard surfaces.