What is this red stuff?

[hllb]

It doesn’t seem like cyano as it’s not a slime. It kind of looks like little disc shaped leaves - one end attached to rock the other sticking up floating in water.

 

[Peach02]

I've got something that looks similar in my tank, it doesn't spread and it seems to glow under certain light

 

[jaxredsoxfan]

That looks like some form of coralline algae to me.

 

[Clear Choice Aquatics]

Does it peel off easily? It looks like coralline to me

 

[hllb]

As long as it doesn’t cause trouble, it’s pretty!

 

[Bret Brinkmann]

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The small red stuff sticking out from the rock looks like a red macro algae. Maybe halymenia or gracilaria. Too small to tell yet. But the other pretty colors are coraline. All of these are good.