Looking at tainte97's pictures you can see how you choose the smaller tub so that it can "stack" somehow on top of the larger "sump" tub. He drilled holes in the bases of his two smaller tubs. you can also cut out the bottoms leaving about a 2 inch border and then place a piece of eggcrate in the tubs. the filter fiber, cotton and bioballs are not heavy and this will be enough to support them. If you go to wallmart and target, you can often find stackable smaller tubs. when you stack them, one inside the other, there is often a space of about 3 -4 inches between the two bottoms of the stacked tubs. this is usually enough to provide an instant chemicle shelf or a shelf on which you have options to place other media in media bags, if you cut out a section of both of the bottoms and replace with egg crate (sold in the ceiling tile section of home depot about 10$ a sheet) He used cord or wire to attach near the top edge of his large sump pulled taught to prevent any bowing which might occur once water is in the sump and then cause the bioball chamber to fall into the sump. I notched pieces of pvc pipe and slipped them down over the edges like a brace in three areas to prevent bowing. this is real easy, no cutting plexiglass, and so far no leaks, no problems.