Green Hair Algae? Something Else?

[RickLRMS]

This is in my invertebrate quarantine tank that has been occupied for about four months now. It didn't really look like the photos in the sticky, except a bit like the second photo of bryopsis, plus it is attached to a piece of the sand bed. I have an ammonia badge that looks good but went ahead and tested for ammonia and nitrites, both zero. I wondered if someone could positively identify it and if I should leave it for the trochus snails as I have a couple-hundred baby trochus. Photo below is under white lights, video under blue/white through a filter. Thanks for your thoughts.

 

[lapin]

Hair gets a bit slimey. Bryopsis is a bit fern like.

 

[RickLRMS]

This, to me, looks fern-like. It is particularly noticeably (to me) fern-like in the video. But both ammonia and nitrites are zero. In any case, if it starts to expand I’ll pull it out. But I was curious as to what it was.