35 gallon rubbermaid. 2 shower floor drains in one end connected to 2" pvc with elbows that extend down into the pond 2' so the water falls down the tubes it brings air with it, it looks like i have an aerator inside the pvc. the water comes in through the lid and i have a figure 8 of 1" pvc with holes drilled all over in it as a spray bar, bio media is 5 bags of poly fill and 4 boxes of bio balls underneath a cut to fit industrial dishwasher rack that holds a layer of filter mat for fine mechanical filtration. initial mechanical filtration is done in the lower section of the pond pre filter. 2 dishwasher racks sandwich a wad of outdoor pond netting that i can remove and rinse. the 40 gallon breeder that is drilled has a bare bottom sits above the lower section of the pond with a pump that draws from right where the water falls from the upper section, it does a great job of settling out detritus that is stirred up in the waterfall. i siphon it out daily or every other day depending on build up.