In order to study what kinds of phytoplankton can grow spontaneously at high nitrogen and phosphorus levels formed from compound fishing feed decomposition, an experiment was carried out in a greenhouse during summer. The experiment included a control group with no aeration and a treatment group aerated continuously from day 12. The results revealed that the aeration significantly improved dissolved oxygen, pH, oxidation reduction potential values, chlorophyll a, and total algal biomass in the water. Chlorophyll a in the control was low but formed a peak from days 10 to 17, while that in the treatment reached its highest value of (1 169.57 ± 1 133.01) μg/L on day 27, and the highest algal biomass was (279.07±339.83) mg/L on day 25. Green algae particularly Scenedesmus spp. dominated in the treatment, and green algae particularly Chlamydomonas spp. and Chroococcus sp. dominated in the control, from days 21 to 31. Therefore, green algae dominated under aeration at high nutrient level of 3.8-22.1 mg/L total nitrogen and 2.1-16.9 mg/L total phosphorus, which was derived from decomposing compound fish feed.