How do you tell Cyano from Purple Coreline?

[oakengineer]

The rock on top is my seed rock. Everything else was dry. I'm a week in cycling. When I bought my seed rock the guy at the store picked it out. I thought the little purple spot was correline algae. But as I do more looking, I'm wondering if it is Cyano bacteria. So, please let me know what it is, and should I be worried.

http://i.imgur.com/KMfsKh1.jpg

[shesacharmer]

Looks like coraline to me.

[kalgra]

Cyano looks like brown reddish to red purple slime. Coraline is hard and is encrusted on the rock. If your not sure just touch it, Cyano will wipe off or blow off easily with a turkey Bastor or power head. Coraline will not.

[mbingha]

Coralline is calcified, and smooth yet hard. Cyano is slimy and can be easily brushed off.

[asudavew]

Cyano will move around in the current. Coralline won't. It's solid IME.

[Mcgeezer]

Coralline takes months to develop. Cyano is slimy and reddish brown in color. Corraline is calcified. Your rocks will actually start turning a greenish color for awhile and then come back to normal. Next thing you know...you'll be scraping it off your front glass every week. My entire back glass and overflow are completely encrusted with the stuff.

Coraline needs good calcium dosing to stay sufficient, otherwise it won't grow, it's also very sensitive to phosphate and nitrate. In a fully established tank, a large bloom of coraline basically tells you your doing everything right.