Need help with an algea, and possibly an octopus?

So the first thing is some sort of algea, It's purple and it webs over all my rocks and it's getting annoying. It hasn't seemed to harm anything.
And the other is a critter in a hole in 1 of my rocks, it's very small.
It has tentacles that are striped black and white, i think it has 6 or so, and when it peeks out of the hole it looks to be breathing? or something lol i dont know, i can't get a good enough view of it. I fed it piece of a silver side and it grabbed the meat and yanked it in the hole..
If you know anything about it let me know.
Thanks
JJ
Maybe the pictures will help.
(sorry best i could do)

 

All I see is Red Slime (cyanobacteria), I dont see any critters.

 

i think your octopus is prob a small brittle star - but i also dont see anything

 

Sorry, im pretty new a this.
Ill get a better picture tonight when it comes out more.
In the pic you can just see 1 of its black and white tentacles.

 

oh i see it now - yep its def just a brittle starfish - nothing to worry about!

 

I'd agree with both of the above replies its a Cyano and maybe a mini brittle star is what you see .

 

Cool thank you.
I will look up the brittle star.
So do i need to continue feeding it? or will it scavenge?
Thanks guys.

 

It will scavenge

 

it could be a bristle starfish too. are you using tap water?

 

Brittle star =) They scavenge about, don't really do much or get very big either, I'm not sure, so don't quote me on this, but I think they get maybe 1/2 inch at largest.

Other is Cyano, get rid of it with a good cleaning!

Good luck!