the other advantage of running additional internals is you can whip them out for your QT tank when you buy new fish
QT setup = internal running in a tank as spare + cheapo tank from a classified ad
21G: ADFs, Amano, Cherry and Tiger Shrimp
50G: Pearl Gouramis, Guppies, Neons, Lemons, Pygmy Cories, Otos, Clown Plec, bristlenose pleco, platies, swords
50G: Tall, bowfront SA setup, Angels, Festivums, Rams, Pictus', Raphael, bristlenose pleco
(10g QT tank)
80g: Mbuna, Red Zebras, Yellow Labs, Blue Cobalts, Lab Hongis, Bumblebees, Syno M.punctatus, Plec