Need an ID please

[Tonkastoy]

As far as the body shape, they look very close. Just a different color pattern.
I am assuming that if this is a type of flat worm, then I probably don't want to put it back in my tank? It is very cool to watch it in the cup it is in but I have never seen it in the tank until now and doubt I would see it again if it was something I could/should put back into the tank. Thank you for the link though. At least it narrows down what it could be

[Van down by the river]

I've had these before in my tanks. I stumble across them when moving rocks or looking at the undersides of rocks and coral.
It seems to be a Pericelis sp.
It seems to be a predator. Most likely feeding on micro fauna and small copepods. It does not appear to bother corals.