Although the species is euryphagic, it feeds predominantly on fish (Schoonbee, 1969; Richter, 1976; Bruton, 1979b; Spataru, Viveen and Gophen, 1987). Its propensity toward a carnivorous feeding habit suggests that C. gariepinus has a relatively high dietary protein requirement, in the order of 40–50 percent of crude protein on a dry weight basis. The fact that the animal also feeds on plant material reflects its ability to digest plant proteins and utilize carbohydrates as an energy source (Clay, 1979; Uys, Hecht and Walters, 1987; Van Weerd, 1995). From a farming perspective, euryphagy holds the benefit that a wide variety of feed ingredients of animal and plant origin may be considered in formulating feeds that will satisfy the fish's dietary requirements. 

The nutritional requirements of C. gariepinus larvae and early juveniles are summarized in Table 4. Common to most species, the larvae and early juveniles (up to approximately 1 g) have a high protein demand of around 55 percent and a lipid requirement of 9 percent. The carbohydrates content can be as high as 21 percent of the diet. A minimum level of 0.5–1 percent dietary n-3 fatty acids has been recommended for Heterobranchus longifilis fry (Kerdchuen, 1992). In the absence of any quantitative information for C. gariepinus and the suggestion made by Uys (1989) that early juveniles grow better if at least 10 percent of the total lipid consists of fish oil, it is recommended that the minimum level as suggested by Kerdchuen (1992) is incorporated into larval feeds.

Some work has been undertaken on the qualitative amino acid requirements of larvae (Conceição et al., 1998), but the quantitative requirements of larvae, except for methionine (Uys, 1984) are not known. Similarly, the fatty acid requirements are unknown, except that a 1:1 ratio of n3 and n6 fatty acids appears to be optimal for growth and body condition. The amino acid requirements of early juveniles and from >10 g bodyweight onwards are better understood and are listed in Table 4.

Uys and Hecht (1987) and Uys, Hecht and Walters (1987) reported pancreatic and foregut amylase activity in C. gariepinus larvae. Similarly, Ali and Jauncey (2005a) found that intestinal alpha-amylase activity increased with increasing dietary carbohydrate levels. These findings show that North African catfish are capable of digesting carbohydrates from an early stage and this persists throughout the animal’s lifespan (Uys, 1989).

The available information on the nutritional requirements for the grow-out phase of C. gariepinus is summarized in Table 4.

There is some evidence to suggest that the nutrient requirements change at around 5 g in weight and remain fairly constant there after. This is largely reflected by a decreasing dietary protein demand. Most of the evidence suggests that the basic nutritional requirements during the grow-out phase range from 40 to 43 percent for protein, 10 to 12 percent for dietary lipid and between 15 and 32 percent for carbohydrate (Table 4). Optimum digestible energy is between 14 and 16 kJ/g and the protein to energy ratio is optimal between 26 and 29 mg/kJ of digestible energy. The essential amino acid requirements of fish >10 g are fairly well understood (Table 4). Both animal and plant proteins are well digested (Tables 5a and 5b) and can be used to varying degrees to replace fishmeal (Table 6) and soybean meal in the diet. Least costing of the diet and appetite feeding schedules have shown that profitability can be optimized at dietary protein levels of between 35 and 38 percent. Much of the above is summarized by Van Weerd (1995). Tables 4 and 5 provide a comprehensive list of pertinent references.

It has been shown that growth is negatively affected if fish oil is used as the sole source of lipid (Ng, Lim and Boey, 2003; Ng et al., 2004), which clearly suggests that the species has a certain requirement for n-6 fatty acids. However, the dietary lipid source does not affect whole-body composition or muscle lipid level in catfish, although fatty acid and alpha-tocopherol levels generally reflect the fatty acid profile and alpha-tocopherol concentration of the dietary lipids that are used (Ng, Lim and Boey, 2003). 

It would appear that the average permissible carbohydrate level is around 27 percent (see Table 4), and Ali (2001) suggests that C. gariepinus cannot utilize dietary carbohydrate levels above 35 percent. On the other hand, Pantazis (2005) found that dietary carbohydrate levels of between 26 and 32 percent had a significant protein sparing effect, advocating the greater use of carbohydrates in catfish diet formulation.

Gross energy and digestible energy requirements are around 19 kJ/kg and 14 kJ/kg, respectively, with an average protein to energy ratio of 27 mg/kJ. The protein to energy ratio is however very much dependent on temperature (Henken, Machiels, Dekker and Hogendoorn, 1986) and increases markedly from 25.4 mg/kJ at 24 °C to 34.7 mg/kJ at 29 °C. Body composition in C. gariepinus is not influenced by varying dietary P/E ratios (Ali and Jauncey, 2005a). At a dietary protein content of 40 percent, it appears that the optimal lipid: carbohydrate ratio is around 1:2.5.

The precise vitamin and mineral requirements of C. gariepinus are poorly understood. Experimental results, however, suggest that the requirements by channel catfish (Wilson and Moreau, 1996) more than adequately cater for the needs of North African catfish. These are listed in Table 4. Under practical pond-farming conditions, the fish obtain a substantial proportion of their micro-nutrient requirements from the environment. Farmers have found that adding a general vitamin and mineral premix such that it makes up 1 percent of the diet is more than adequate to fulfill micro-nutrient requirements. A more recent study by Ng, Ang and Liew (2001) has shown that mineral supplementation of feed containing 27 percent fishmeal had no beneficial effect on growth of juvenile C. gariepinus. They suggest that it is not necessary to include a mineral mix into diets that contain a high proportion of fishmeal.