Supplementing high levels of dietary crude protein in the absence of amino acid balance and enough energy in fish diets may results in reduced growth, improper feed intake and poor protein utilization efficiency coupled with unviable feed costs and adverse environmental effects due to high nitrogen excretion. It is necessary to improve the dietary protein quality to avoid unnecessary nitrogen excretion, and the use of protein as an energy source by fish, quality and determine proper dietary protein to energy (DP:DE) ratios in order to maximize protein utilization efficiency. It will help the aquaculture sector to obtain better growth response at a low-cost and without any adverse environmental effects. In the present article, we have deliberated in detail the previous and ongoing researches about protein research in fish nutrition. Besides, we have made a comparison between two so far commonly used methods in protein research, i.e., the graded supplementation and diet-dilution technique. According to the data presented here, is focusing on the formulation of balanced diets, the diet-dilution technique seems to be more accurate than the graded supplementation method. Thus, future studies should be focused on the use of diet-dilution technique along with proper dietary protein to energy ratios in order to formulate well-balanced diets. These attempts will significantly improve the protein and energy research in aquaculture nutrition. Moreover, feed industries will become able to formulate biologically balanced and environment-friendly diets at a low cost.