Congenial water quality is a key issue for increasing the growth, health, and physiological performance of aquatic animals. In Bangladesh, lime is generally used in aquacultural ponds for improving water quality. Both agricultural lime and eggshell are consisting of calcium carbonate. Therefore, eggshell powder (ESP) can be used as alternative of lime. The objective of this study to examined efficacy of different poultry ESP as an alternative to lime for purifying water quality of aquaculture system. An in vitro trial was conducted to determine the effect of contact time on water
quality using different eggshell powders. Five treatments were employed: hen eggshell powder (T1), quail eggshell powder (T2), duck eggshell powder (T3), lime (T4) and a control treatment without eggshell powder (T5). Each treatment consisted of three replicates. One liter of clean tap water was placed in each experimental cylinder, after which clay particles were added at a concentration of 1 g/L. Eggshell powders and lime were incorporated at a rate of 30 mg/L. Water quality parameters were monitored at 6-hour intervals for 72 hours. Results demonstrated that majority of the physicochemical parameters altered rapidly during the initial phase and stabilized after 48 h. The T4 group showed the significantly highest values of TDS (45 mg/L ), EC (102.33 μS/cm), pH (6.8) and hardness (75.66 mg/L), while T3 exhibited the greatest water transparency (11.33 cm) compared to other treatments. No notable variances (p>0.05) were found in the water temperature and dissolve
oxygen, while ammonia, nitrate and nitrite remained negligible throughout the study. Overall, ESP revealed comparable effects to lime in bolstering major water quality indices, particularly by enlarging mineral contents, buffering capacity and transparency. These findings suggest that ESP
can serve as a cost-effective, eco-friendly and sustainable alternative to conventional liming agent in aquaculture systems.