Ameliorative effects of zeolite and yucca extract on water quality, growth performance, feed utilization, and hematobiochemical parameters of European seabass reared at high stocking densities

The aim of the present study was to evaluate the efficiency of natural zeolite (Z) and Yucca schidigera extract (YE) as water treatments for European seabass, Dicentrarchus labrax, reared at high stocking density. A factorial design was conducted using two socking densities (100 and 200 fingerlings/m3) and five water treatments (control, zeolite 10 g/L, zeolite 15 g/L, YE 0.75 ml/l, and YE 1 ml/L). The fish (with an initial weight of 5.83 g) were allocated into 1 m3 fiberglass tanks in triplicates per each treatment and fed a commercial diet for 45 days. The results demonstrated that rearing European seabass at a high stocking density (200 fish/m3) caused a significant deterioration in water quality parameters, such as dissolved oxygen, NH3-N, NH4-N, NO2-N, and NO3-N by 11.11 %, 49.5 %, 33.33 %, 38.46 %, and 9.09 %, respectively compared to the low stoking density. Furthermore, increasing the stocking density of European seabass significantly reduced growth performance, feed utilization, and various haemato-biochemical parameters. The water treatment with both zeolite and YE significantly improved dissolved oxygen levels and decreased the nitrogen derivatives in tanks water of low and high stocking densities. Also, the water treatments ameliorated the effects of increasing stocking density on fish growth performance, feed utilization, hematological, and biochemical parameters. Whereas the highest wight gain (32.17 g), survival (93 %), and best FCR (1.9) were recorded in group treated with high zeolite level at low stocking density. Regarding the efficiency of both water treatment materials used in this study, water treatment with zeolite at the highest level (15 g/L) outperformed YE in different evaluated parameters of water quality, fish growth, and physiological performance. The mean effects of zeolite and YE at high levels showed an improvement of weight gain and feed conversion ratio by 103.68 %, 46.37 %, 30.90 %, and 23.47 %, respectively, compared to the control. Moreover, the effects of each substrate were level dependent. In conclusion, the water treatment with zeolite and YE could improve the wellbeing and production of seabass fish in favor of zeolite (15 g/l). •Two environmentally friendly methods were applied to control water quality deterioration at high densities.•Natural zeolite and yucca extract were used as water additives in the European seabass rearing water.•Both additions succeeded in overcoming the effect of high density on water qual