can anyone tell me what species of brittle star this is and it if would be compatible with an O. Cyanea? initially i thought it would be fine until i read about green brittle stars being highly aggressive and bad tankmates. it was found in queensland australia and hitched a ride into my tank with my live rock (along with several others). its arms are roughly 8 inches long and when my octopus arrives i am expecting it to be between 2 and 4 inches. one of the reasons i think it might be ok, even if it is somewhat aggressive and tries to steal food from the octopus is it heads for cover as soon as i turn the lights on and the cyanea is diurnal, so they shouldnt cross paths, unless it tries to eat the octopus in its sleep or something. also, does anyone know what that weird round thing is underneath it? my tank is still cycling so if the water quality etc looks horrible thats probably because it it. i finally turned my skimmer on today and im shocked at how quickly and how dramatically its made a difference.