The current study was conducted at the Agricultural Research Station-Al-Hartha (Agriculture College, Basrah University) in Al-Hartha District, approximatley 16km to the northeast of Basrah Governorate. The experiment was conducted in four earthen ponds (2500m²). These ponds were drained for one month; one ton of organic fertilizers (Buffalo dung) was applied in each pond before refilling with water. After one week from refilling, 10000 common carp larvae with an average weight of 0.104± 0.002g were stocked in each pond. No artificial food was supplied to the fish during the experiment. Fish growth recorded a high rate at the beginning of experiment, then decreased or ceased at the end. The total number of phytoplankton was low at the beginning of the experiment, while a gradual increase was detected during the study. A negative correlation was found between the total number of phytoplankton and fish growth in all ponds. In addition, a significant positive correlation was recorded between salinity and fish growth. The investigation of phytoplankton taxa in the four ponds revealed that the first important family was Bacillariophyceae followed by Chlorophyceae.