To maintain pond water quality, a large amount of wastewater is discharged. The wastewater degrades the environment and annoys nearby residents. This wastewater is the potential for growing Azolla microphylla, a valuable floating fern for different purposes. This research aims to observe the effect of water replacing period and mechanical aeration on the growth of A. microphylla and the wastewater quality. A 20-gram of A. microphylla biomass was inoculated in a plastic-layered wooden box (50×30×20cm) filled with catfish pond wastewater, and then designed treatments were applied for a 12-day experiment. A completely randomized design with two factorial arrangements was implemented. The first factor was the period of water replacement consisted of four levels: no replacement (E0), once in 2 days (E1), once in 4 days (E2), and once in 6 days (E3). The second factor was mechanical aeration consisted of three levels: no mechanical aeration (A0), 12-hour aeration (A1), and 24-hour aeration (A2). Parameters to be observed were Azolla biomass and water quality (temperature, pH, turbidity, and ammonium). The data set was analyzed using ANOVA followed by LSD multiple comparisons. Results revealed that interaction of the water replacing periods and the mechanical aeration significantly affected water quality (temperature, pH, turbidity, ammonium) but was not significant for the yield of A. microphylla biomass. The factor of water replacing period alone significantly affected the growth of A. microphylla. The E2 treatment was the most promising option, with a biomass yield of 804 g/m2 within 12-day cultivation.