This paper discussed about the effect of Zoogloea ramigera on the initial microorganism attachment and the biofilm growth. The additions of 5, 10 and 15%(w/w) of Zoogloea ramigera were facilitated for the initial attachment on the surface of the acryl disk. At biofilm growth, the more Zoogloea ramigera added to the activated sludge, the more biofilm dry weight was obtained. In order to get the stable biofilm and to minimize the start-up periods, initial biofilm formation using activated sludge with floe forming microorganisms like Zoogloea ramigera was recommended rather than that without floe forming microorganisms.