This is one my sand sifting stars...they are pretty active little guys...a lot of times you can see the substrate really moving as they get around underneath...but they also get up on the glass occasionally and into the rockwork. the brittlestar has been more elusive, even with just the moonlighting on he doesn't come out all the way...he found himself a little hole and seems to like it there
the little specs on the glass are copeopods
K