Effects of Total Hardness on Growth Performances, Survival and Feed Utilization Efficiencies of Platy Fish (Xiphophorus maculatus)

Abstract

The effects of total hardness on growth performance, survival, and feed utilization efficiencies of platy fish (Xiphophorus maculatus) were studied. Twenty-one days old 180 juvenile fish with initial mean weight of 0.11±0.04g and mean total length of 1.82±0.21cm were exposed to three different hardness levels as, 50, 150, 250 mg/L and 0.00mg/L as the control. Fish were randomly assigned to three treatments and the control each with three replicates. All the fish were kept in 50 L glass tanks at initial stocking density of 15 fish/tank. Total hardness of the water was maintained by adding CaCl2 & MgCl2 into the water. Fish were fed with commercial prima diet (39% crude protein) twice per day to near satiety and experiment was lasted for 06 weeks. Water quality of each treatment was maintained below the lethal levels. The percentage survival of fish in each treatment was observed and recorded daily. Total length and body weight of fish in each treatment was measured every two-weeks, while amount of feed consumed was recorded daily. At the end of the experiment, % Average Daily Gain (%ADG), % Specific Growth Rate (%SGR) and Food Conversion Ratio (FCR) were calculated to evaluate the growth performances and feed utilization efficiencies of platy fish. At the end of the experiment, significantly greatest (p<0.05) mean weight gain (0.54±0.01 g), mean total length gain (1.57±0.05 cm), %ADG (11.62±0.21), %SGR (4.20±0.04) and significantly lowest (P<0.05) FCR (1.54±0.05) were observed in 150 mg/L hardness level. Among tested three levels, the growth performances were significantly highest in the hardness level of 150 mg/L followed by 50 mg/L. Final percentage survival was not significantly (p>0.05) different among treatments. According to the overall results, significantly highest and lowest growth performances were observed in 150 mg/L and 250 mg/L hardness levels respectively, while moderate growth performances were observed in 50 mg/L. Correlation coefficient between the total hardness and %SGR of fish was 0.818 and it clearly showed that, around 150 mg/L total hardness level is more favorable for the growth of platy fish. Results of this study revealed that, 150 mg/L total hardness level is the best tested levels for the growth performances and feed utilization efficiencies of Xiphophorus maculatus. However, above, and below 150 mg/L total hardness levels are negatively affected the growth performances & feed utilization efficiencies.