#hitchhicker

I came back from a coral show where one of the vendors had a couple of these snails in with their soft coral display, I'm assuming to contain algae. When I got home, I noticed a little snail hitchhiker...I'm assuming a trochus snail? I've decided for the moment to name her Fred. For now, I'll...

I've had small amounts of this algae growing on my rock. Can anyone ID it and is it likely to be invasive? Notes in: In one of the images, the algae is in the bottom left corner of the image with a trochus snails to its right for scale. The other image shows a small colony of it growing in a...