What is dark purple and furry?

[MysterioMask]

I have this dark purple fur like something on a few things. It seems to grow in sort of a sheet. When it starts it starts out near black but as it gets bigger it takes on this deep purple. Color. And looks a lot like fur. Sticks well to turbulent surfaces and will come off in large chunks of directly agitated. What is it and what eats it?*

 

[54seaweed]

suck it out with a siphon during water change , it looks sort of like red turf algae