Is this coralline on my SPS?

[aleok]

Was purchased about 6 months ago as a "Table green SPS" (that's all i know). Over the last 1.5-2 weeks I've noticed this strange discoloration, light purple, coralline like, spot developing. It's barely grown during the 6 months, the base has only spread onto the LR. Tank is stable, everything else, except a Duncan that hasn't opened in 3 days is fine. Any ideas?

 

[aleok]

anyone?

 

[MarkL]

its hard to see the picture. But coralline can grow on a dead skeleton if the tissue is gone.

 

[aleok]

maybe a bigger pic can help. there's no dead tissue, i think..