Ufff, tough to say. They could be planaria, but they could be a lot of other things too. It will be otugh to cutback on stuff to feed them tho....
I was going to say there likely isn't much in the way of organic waste in this tank, but is the sand clean or is there a leetle cyano in there ....? How long has it been up, and how's that sand bed looking?
Is that a gorgonian in there - is it meant to be alive? It looks to me like yes and yes but frankly it's pretty much certain to starve to death. The nonphotosynthetic ones are very hard to feed - the phytoplankton 'mixes' you get at the store are just so much pollution in a bottle for these guys. They need big tanks with big refugia to keep them going.