Protein content behavior under relative low carbohydrate content, offered better growth values than relative high carbohydrate content, not only in biomass gain (Fig. 1), but also in all the other parameters measured (individual weight gain, SGR, FCR, and FCE). Survival had a punctual significant exception in 20% CP with C low (62.5%). Highest values were significantly recorded at 30% CP for biomass gain, FCR and FCE. For SGR, FCR and FCE, 30% CP was significantly different to 20% and 40% CP. For survival at C low significant differences were presented in all CP content, being 30% CP the best. At relative high carbohydrate content, there were no significant differences between protein contents. Curves for relative high carbohydrate content showed more flattened tendency form than relative low carbohydrate content.