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These are important energy source for fishes and also contribute to the taste of fishes. Like some of the aminoacids, there are also essential fatty acids, which have to be supplied through the dietary lipid source since thesecan not be synthesized by fish. Polyunsaturated fats are more beneficial for fish. Linolenic (n-3) and Linoleic acids(n-6) are important for both the groups of fish and shrimp. The requirement of fat varies from species to species.Carbohydrates:Carbohydrates are the cheapest source of energy in the feeds. Starch : sugars, cellulose, gums are usually the typesof carbohydrate sources. Fish are known to utilize simple carbohydrates like sugars more effectively than complexstarches, while the shrimp are known to better utilize the complex carbohydrates. Carnivores are not efficientconverters of carbohydrates. Catfish and several species of carps are known to utilize complex carbohydrates andsome carbohydrates are normally not digested and these include fibers. Herbivorous fish are able to digest fiberbecause of the cellulase enzymes present in them. Fish in general are known to be not efficient utilizes ofcarbohydrates. However, this view is changing rapidly with the demonstration of efficient use of carbohydrates incarps and other groups of fishes.Energy:Like all other animals, fish also require energy. However, fish use much energy for protein synthesis than do warmbloodedanimals because they do not need to maintain constant body temperature, need less energy to maintainposition and less energy is used for excretion of ammonia. Optimum energy level is important in both fish andshrimp feeds. This energy required for maintenance of the body is obtained from burning protein, fat orcarbohydrate. The energy thus liberated is used for mechanical work (muscle activity), chemical activity (chemicalprocess taking place in the body); electrical work (nerve activity), osmotic work (maintaining body fluids in anequilibrium). Free energy is that which is left after using it for the maintenance of the biological activity. The energylevel in the feed is calculated using the standard values available for the principal energy source components namely,protein - 5 Kcal/g, carbohydrate- 4 Kcal/g and lipid - 9 Kcal/g. Higher energy in the feed results in the less consumptionof food and thereby resulting in less protein available for growth. Also, addition of excess fat results in theaccumulation of fat in the body and bad odor. When the energy levels in the diet are less, protein is used up tomeet the energy needs and consequently result in the poor growth of fish.With the Increase in knowledge in fish nutrition, lipids and carbohydrates are increasingly used to spare protein forgrowth. In carnivorous fish diet by including fat as energy source at high level, protein is made available forgrowth.Vitamins:Both water soluble as well as fat-soluble vitamins are essential for prawns and fishes, Vitamins are complexorganic compounds required in trace amounts for normal growth, reproduction, health and metabolism. Fat-solublevitamins are recognized to be important in many ways for the animal for breeding, development, disease resistantetc. and Vitamin E has been found to be important for reproduction. Vitamin C has been found to increase diseaseresistance and improve the growth of fishes.Minerals:These are considered to be important both for body function and growth, They are important in providing rigidity andstrength to the bones of fish and the exoskeleton of crustacean, The body fluids are involved, in the osmoticregulation, nervous and endocrine system. Seven major minerals, namely calcium, phosphorous, potassium,chlorine, sodium, magnesium, sulphur, manganese, nickel, cobalt, molybdenum and selenium are needed to be ina balanced diet. Fish and Crustacea absorb minerals from the water through skin and gills, Calcium is rich in99