Stars

I'm not sure what the one with the red stripes is, but it seems that most of the small starfish that come on most liverock are usually harmless.  There are tiny brittle stars all over in my tank and they grow very slow.  I've got other tiny starfish that have six arms.  For the most part they all hang out in the substrate and macroalgae in my tank and never seem to make there way on to any of my corals.  Its hard to say without looking at them, but typicaly I have learned that the smaller stars pose no threat to corals.  But if they get bigger they may.  There are some stars that remain small forever and only reproduce as their form of growth by spliting.  Also these stars almost always remain out of site.  The ones in my tank seem to do no harm, but if you have some that are always visible, watch them and sometimes at night you should check on your tank and see if they have any interest in your corals.  Even if I tryed to get rid of all the stars in my tank I would still find some pop up here and there anyway.  Just keep an eye on them.