Is this a kind of algae?

[Dw79]

Spotted this on my glass today, is this a kind of algae? Or something else?

 

[Reefer40b]

probably coraline, try to scrap it if its hard then its coraline

 

[TriggerFinger]

It looks like a snail operculum.

 

[Dw79]

probably coraline, try to scrap it if its hard then its coraline

Ok, thanks. Just wanted confirmation first in case I scraped it and spread some kind of unwanted particals around the tank

 

[Dw79]

It looks like a snail operculum.

I thought maybe a snail at first, but when I looked from the side, it's completely flat

 

[Dw79]

It looks like a snail operculum.

You were right. I figured it would have something hanging of the back, if one of those came off. I scraped it and it came off all in one piece and floated around.
Thank you!!