What is this?

[Wwidener]

This showed up in my tank last night. Is it anything to be worried about? It's soft, almost mushy but stuck to the rock.

[Sniperhank]

Looks like the other form of flower pot. Can't think of the name. Starts with an a I think.

[54seaweed]

are you referring to the coral or all the white stuff

coral looks like a flower pot
the white stuff looks like sponge I would recommend removing it before it invades the coral

[Wwidener]

Yeah, the white stuff. How would I remove it? A toothbrush?

[Wwidener]

I also have dark red algae growing on this rock that does not come off. How do I get that off?

[Sniperhank]

Looks like sponge growth. I'd guess you could toothbrush it off, but most likely it'll keep growing back.
As for the dark red, is it slimey or hairy? You can manually remove as you stated, but make sure you siphon out if it is an algae.

[Wwidener]

It's neither slimy or hairy. Red coraline? I toothbrushed the white stuff and it came off well. I'm taking it to my LFS today to see what they have. Check this out on my brain coral. Idea? It closes up when I touch it..

[Sniperhank]

Not coralline. That is a macro algae though. Coraline doesn't normally branch up. The name of it is currently escaping me, but here is an Id link I keep on my phone.
http://melevsreef.com/critter-id