Is this a sponge or algae?

[LondonReefer]

Hi all,

Noticed this thin strand growing on my glass. It's just over half an inch now, but that's probably only taken a few days to grow. Can easily pull it out but thought I'd get it identified.

Thanks for any help

 

[cloak]

It kind of looks like the roots of some sort of macro algae. Weird that it's growing against the glass though.

 

[jerrod]

I have a sponge that looks like that that is orange colored but it’s only under rocks away from light. Not sure what that is though since it’s on the glass in a lit area.

 

[Paul B]

Sponge, I got dozens of them

 

[El_Guapo13]

Lol looks like roots. But probably a sponge. Sponges are weird that way.