This study was carried out for determinate the phytoplankton distribution and the water quality of cultured sea bass land ponds, in Mugla province, Turkey. Sea bass (Dicentrarchus labrax, L., 1758) is known the most popular species of the Mediterranean region and its production has been multiplying since the 1980s. Water samples were taken from 6 different points, including main drainage, clean water, and 4 land ponds, to identify the phytoplankton composition. Samples were collected on May 2017 from the fish farm when algal blooms were observed. A total of 31 taxa belonging to Bacillariophyta (13), Charophyta (1), Chlorophyta (7), Cryptophyta (2), Cyanobacteria (3) Euglenozoa (4) and Ochrophyta (1) divisions were identified. It is stated that excessive algal blooms may cause massive fish deaths in aquaculture ponds. According to the recorded species of phytoplankton, the ponds are fairly organically polluted. Also, Microcystis aeuruginosa and Merismopedia glauca of toxin-producing cyanobacteria were recorded often in water samples. Especially when Cyanobacteria members do excessive blooms, this may be a big threat to the fish farm living beings. In conclusion, monitoring and controlling the phytoplankton composition and water quality parameters are required periodically to improve the conditions of aquaculture.