## 4 Discussion  
In the present study, the long-term effects of leanordite mineraloid dietary additive were tested in _C. gariepinus_. In total, fish were fed with four HS inclusions (HS0, HS1, HS3, and HS6) for a six-month period from juveniles (BW 28.1 \(\pm\) 6.2 g) to adults (BW 733.0 \(\pm\) 202.9 g). Firstly, the fish were exposed short term to HS dietary additives for a 56-day period (see published manuscript [35]) while the present study observed the prolonged long-term effects of the HS dietary additive on overall performance of intensively reared _C. gariepinus_. During our study, the experimental fish doubled their initial BW and reached a final size that is considered an average market size for _C. gariepinus_ sold in African countries [46]. However, no significant positive/negative effects of leanordite HS dietary additive (that was spray coated on commercial feed pellets) were observed on growth and production performance of _C. gariepinus_ in our study. Based on our studies, it seems that the short-term and even long-term leanordite HS dietary exposure had no beneficial/detrimental effects on _C. gariepinus_ growth performance from juvenile until market-size stage. Similarly, as in our study, [PERSON] et al. [33]. found no effects of HS dietary additive on fish growth performance, while other authors [18; 31; 32] described beneficial effects after short-term (maximum 10 weeks) HS dietary exposures. Furthermore, no positive/negative effects in the somatic indices (VSI, GSI, HSI, SSI, VFSI, and GaSI) were observed after long-term HS dietary exposure. These indices were assessed as indicators of fish health and physical condition that might be negatively affected in relation to stress and body detoxification (e.g., liver and spleen of larger size), but they were at a physiological optimum as they did not differ from the control group. By the end of this study, most of the sampled fish (93.8%) were sexually mature, which is typical for _C. gariepinus_ of this average size (BW 733.0 \(\pm\) 202.9 g). Overall mortality reached 9.3-25.3% HS0-HS6 groups by the end of our study. This result corresponds to a mortality range of 16.7-55.7% that was reported by [PERSON] et al. [47] for juvenile _C. gariepinus_ reared under different stocking densities for 42 days. In the present study, the final product yield of fish (i.e., weight of eviscerated fish, head, and fillets with/without skin) was assessed. The eviscerated fish yield was 90.4-92.3%, the head was 22.9-25.2%, the fillets with skin were 49.0-51.7%, and the fillets without skin reached 41.5-42.7% of the fish BW. These results are in accordance with findings of [PERSON] et al. [26] who presented a 40-43% fillet yield without skin after testing different commercial diets. While the yield of eviscerated body and fillets without skin did not differ significantly between the tested groups (HS0-HS6) by the end of the present study, the weight of head and fillets with skin differed--this finding might be a result of the slightly lower size of filleted fish in group HS6, and probably therefore even the head yield was slightly higher in this group compared to the control. According to results from the main composition of fish meat, the content of ash was continually decreasing with the increasing water content in fish muscles and increasing Humafit concentration in the fish diet from groups HS1 to HS6. This finding corresponds to the assumption that the higher muscle water content corresponds to the lower ash content in muscle samples. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Experimental Diet** & **Total Polyphenols (mg g\({}^{-1}\))** & **Flavanols (mg g\({}^{-1}\))** \\ \hline HS0 & 4.7 & \textless{}1 \\ HS1 & 4.9 & \textless{}1 \\ HS3 & 6.6 & 3.4 \\ HS6 & 7.3 & 2.3 \\ \hline \hline \end{tabular} Note: HS0\({}^{-}\)control pellets without Humafit supplement, HS1—pellets with 1% of Humafit supplement (1 g/100 g), HS3—pellets with 3% of Humafit supplement (3 g/100 g), HS6—pellets with 6% of Humafit supplement (6 g/100 g).  
\end{table}