Coralline algae or caused by red flatworms ?

[Rmckoy]

Curious if red flatworms cause reddish circles in the glass ( eggs )
Or is this coralline algae ?

 

[Murica]

Coralline

 

[rkpetersen]

Agreed, probably coralline algae, but I'd check by running my tank scraper across it. Coralline will take a few scrapes to remove.

 

[JGT]

The latter.

 

[Rmckoy]

I was assuming coralline , it’s a new tank but older established system .
Currently battling the plague of flat worms