Kelly, the purple thing looks like a kind of worm that lives in the rocks and extends it's feeding tentacles out to the surrounding area. Touch the tentacles and see if they retract or not.
Just seems to be on the one rock (so far) but didn't so much as twitch when I was pokin and proddin it or when I moved the rock. Almost like its not a critter at all...Huh...I'll get a pic in a sec.Some of it is purple cyanobacteria and coral eating white worms - 4 guesses at the rest - either aussie purple tube worms, purple tube anemone's, juvi Bonaire purple sponges, and or saltwater hydras