Assessing the impacts of zeolite on water quality, growth performance, heavy metal content and health condition of farmed tilapia (Oreochromis niloticus)

The rapid expansion and intensification of tilapia (Oreochromis niloticus) aquaculture in Bangladesh results in an increasing tendency of administering more pharmaceuticals in fish health management. Hence, with the aim of investigating the effects of zeolite (a water and sediment treatment compound) on water quality, growth performance, hematology, gut microbial content, and heavy metal content of Oreochromis niloticus, an experiment was performed for 126 days in six experimental earthen ponds (each pond size is one decimal). The stocking density was 300 fry/decimal. Zeolite was applied directly into the water in treatment ponds at a rate of 200 g/ decimal during pond preparation and 100 g/decimal/15 days intervals during the culture period as recommended by the manufacturing company. The results indicated that zeolite had a significant effect (p < 0.05) on all growth indices assessed in all three experimental stages (0-42 days, 43-84 days, 85-126 days) in treatment ponds compared to control ones, except condition factor (CF) at the first stage. Hematological results implied that the application of zeolite in treatment pond water had no significant effect on the red blood cell (RBC) and white blood cell (WBC) of experimental fish blood compared to the control. However, a significant effect on the blood glucose level and total viable count (TVC) of the experimental fish gut was observed due to the addition of zeolite in the treatment ponds. Zeolite supplementation in treatment pond water significantly reduced the concentrations of different heavy metals in pond sediment, water and fish flesh compared to the control. Therefore, zeolite could be recommended for administration in aquaculture. Further research is required to find out whether a higher or lower dose of zeolite improves the water quality, growth performance and health condition, and decreases the heavy metal content of fish or not.