author(s)
Md. Mokter Hossain, Shila Akter, Md. Azharul Islam, Md. Sabbir Hossain, Saker Mohammad Ibrahim Khalil, Md. Abdullah-Al-Mamun and MM Mahbub Alam

abstract
Aquaculture practices in Bangladesh are growing very fast. Different culture systems are being practiced for different fishes. These culture systems have different management practices and profit levels. Chandpur and Lakshmipur districts in Bangladesh became famous for carp polyculture and other fish farming in the recent years. The study compared the farm management practices, disease prevention and disease control, including the profitability among Carp polyculture, Stringing Catfish (shing) and Vietnam koi farming systems in Bangladesh during August 2019 to July 2020. Data about management, production cost, the prevalence of diseases, and benefit of the three culture systems were collected from nine farms (three from each culture system). Among these three farming systems better management was found in carp polyculture, where in carp polyculture 19,513 individuals were stocked in a hectare composed of Tilapia (9,880 individuals ha^-1), Catla (494 ind. ha^-1), Rui (1,974 ind. ha^-1), Mrigel (988 ind. ha^-1), and Common Carp (2,470 ind. ha^-1). Stocking density of Vietnam Koi and stringing catfish (Shing) were 203,035 and 329,251 ind. ha^-1 respectively. The highest net profit was found in Shing monoculture (696,893 BDT ha^-1) followed by Carp polyculture (181,450 BDT ha^-1) and Koi farming (128,440 BDT ha^-1). The production of all farming systems was significantly different from each other, but the net profit of Shing farming was significantly higher than carp polyculture and koi culture (p<0.05). The most common diseases i.e., fin and tail rot, argulosis, epizootic ulcerative syndrome (EUS), nutritional and environmental problems were found during the farming period. As preventive measure farmers used NaCl, CaCO₃, and KMnO_4. For the treatment of diseases, Benzalchronium Chloride 80% solution, Vimermectin BP 1% solution, Ascorbic acid, etc. were used. The outbreak of fish disease, unexpected flood, and excess leasing cost, high feed price, low fish price, etc. were identified as major concerns in fish farming. Farmers can use this information of this study for appropriate management of aqua-farms, prevention and control of diseases, and the selection of profitable culture systems.