I used a 20 gallon tank and built a rack system out of 1/2" pvc to accomodate 4 trays of bio balls and ceramic rings. They sit on egg crate in layers and the top layer is where i put my media bag....bio-chem zorb or chemi pure. The only drawback to my build is water noise. The overflow hose dumps directly into the top media tray and u can hear splashing. But I tolerate it.