Need help identifying some critters

[Hypancistrus]

We have a bit over 60 lbs of liverock in our 8 month old 29 gallon reef. Of the 60, about 10 lbs of it was "high quality" liverock that came packed with all sorts of weird critters, including a live, and very large, mussel of some sort that seems to be thriving. We have a few easy corals, including some xenia, a hammer coral, and a bunch of different types of polyps.

We've also seen some not so welcome things, like flatworms and coral eating slugs, which we've removed as best we could. Two things we've not yet been able to identify. The one, a large yellow limpet looking critter, is getting quite large. We call it "Lemondrop" and I am concerned at how quick it is growing. It has some flesh around the edge of its "shell."



The second looks more like a traditional shelled limpet, like the kind you see in a tide pool.



It seems like in reefs a lot of cool creatures end up eating your corals, then your crabs, then the fish, and finally emerge from the tank in the dead of night to consume your family, and the dogs too. Hopefully neither of these fall in that category. We'd be thankful for any thoughts on what these two might be.

[Hypancistrus]

No ideas?

[Reefing Madness]

I looked, but have no idea. Your on the right track with Limpets, I just could not nail down which ones. Sorry.