Need some recommendations on some good sump/refugium inhabitants. My sump has a bunch of caulerpa, about 3" deep sand, 2'x1' sand surface, very low water flow,no rocks, miracle mud sand substrate, diurnal light cycle of about 11 hours, lots of detritus that originated from I don't know where(possibly bacteria residue or dead bacteria), water depth from sand to surface varies but on average is 7" deep. Is there anything that will thrive in these conditions and not kill too much fauna in the sand bed? Cucumbers, starfish, etc?