I have used strong closepins to keep the graters in place (I have them hanging into the water from a plastic planter in order to keep the metal clips from the battery charger from getting in the water) and have them standing side by side 1" apart. I'll try to do the different placements like you did and see what happens. Mine have no plastic around them. I bought the flat ones with just a black handle and cut that off. I'm still getting mostly red scum with what I think may be dead skin flakes in the water. Last night I tried using 1 T. of Sea Salt and not much happened.