My 6 gal nano finished cycling a couple of weeks ago. The only thing I introduced recently was some cheato in a fuge. Today I find a bunch of these - on the glass, live rock, etc. The largest (pictured) is about 1/4 inch, or a bit less. They move like the entire front half of the thing is a mouth. Are they planaria? (I thought those were red/brown). Could some of my snails have reproduced? I have one large Trochus, three medium ceriths, three small nassarius and two moderate-sized margaritas. They do look like they are grazing on algae...