Sorry for the long delay but sadly life gets in the way sometimes. It is very light with no substance at all and breaks apart very easily. I strongly suspect it is cotton candy algae. I do have a refugium with chaeto in it with practically no measurable nitrate or phosphate but yet it continue to thrive all over my tank even after I remove as much as I can. LED lights are only on for 8 hours. I've read that mexican turbo snails are about the only effective way to control it. Just wondering if anyone else has had luck with anything else.