i think the ring is so you dont get flakes all sticking round the water level in the tank and to stop it all getting washed under when it goes near your filters spray bar or whatever. i think i will get one cause it s***s me when half the food is wasted. my fish are fussy they wont eat it on the surface or the bottom it has to be floating around. only the 2 female guppies and the 2 angels will touch the surface. and no i leave my filters on and just push the spray bar under water till the food is gone.