## 4 Discussion  
To investigate the effect of colored light in the Nile tilapia fingerlings, the parameters that were not related to the light color were kept constant, but there were slight experimental variations in these parameters that are expected not to significantly change this condition of the research. The mean water temperature was maintained at less than 1 \({}^{\circ}\)C of variation, and all the tank water temperatures were in accordance with the optimum range for the growth of the Nile tilapia fingerlings (26-30 \({}^{\circ}\)C), as indicated in [35]. The mean water temperature in the four treatments was 28.50 \({}^{\circ}\)C, which is very close to the ideal temperature of 28 \({}^{\circ}\)C, as reported in [36]. The dissolved oxygen value did not have a very significant variation between all the groups and it was above the level that was acceptable for Nile tilapia (4-5 mg/L), in accordance with [37]. The pH fluctuated between 7 and 8 during the experimental stage, which is the most appropriate range in tilapia aquaculture to obtain the optimum growth and survival rate, as recommended by [38]. The pH value was not different between the R, G, and B groups, which could be because of a greater total amount of bacterial activity that is influenced by the use of artificial light compared to the Natural group. Using a C/N ratio of 20, the TAN concentration has a  
Figure 5: Box-and-whisker plots showing the nutritional composition of the biofloc (%). similar behavior value to pH and it was maintained at levels that are suitable for Nile tilapia, according to [39]. The \(NH_{3}-N\) values did not exceed the levels that were considered lethal for Nile tilapia during the experiment, and this value remained below the recommended limit of 0.1 mg/L [40]. Light color was the only intentionally different parameter among all treatments. Therefore, each treatment was only influenced by a certain color or wavelength of the light. There are not many studies reported of the influence of colored light on the growth of Nile tilapia and fish of different species in general [18], and as far as we know, this is the first study on the fingering stage of development of tilapia. Even more, all previous studies on light effect use other experimental conditions, which include significant differences in: The lack of biofoc, the type or duration of photoperiod, the temperature, the light intensity, peak wavelengths, light spectrum shapes, etc. In this research, we studied the effect of colored light in Nile tilapia fingerlings and biofocs, the R light treatment was the aquaculture system that showed superior performance in many aspects. All the groups received the amount of food according to the biomass that was present in each tank. It is possible to ensure that the R treatment presented the best growth performance because it obtained the best values of total biomass gained, SGR, and DWG. Additionally, there was a great demand for feed intake; when food was provided it was consumed immediately, which was confirmed because the R treatment had the best FCR of 0.8. This is consistent with [41], where feeding conduct was analyzed, but in juvenile Nile tilapia under other experimental conditions, showing (in terms of time (seconds), and chemical cues) that feeding motivation was higher in their red light environment. As well, a similar behavior was found in adult rainbow trout [42], where the growth of fish was increased at red illumination under other experimental conditions, showing low cortisol levels in their blood (less stressful environments). Nevertheless, the G light environment showed the second-best weight gain, but also had the lowest survival. It is possible to rule out that the low survival was caused by a peak of ammonia and TAN, because during the period in which these fish deaths occurred, measurements of ammonia and TAN were in the optimal range for the life of tilapia.