Cir 97 Preparing Your Own Fish Feeds1 Juli-Anne B. Royes and Frank Chapman2 Introduction Nutrition and Feedstuffs Most fish farmers and ornamental fish hobbyists buy Nutrients essential to fish are the same as those required by the bulk of their feed from commercial manufacturers. most other animals. These include water, proteins (amino However, small quantities of specialized feeds are often acids), lipids (fats, oils, fatty acids), carbohydrates (sugars, needed for experimental purposes, feeding difficult-to- starch), vitamins and minerals. In addition, pigments maintain aquarium fishes, larval or small juvenile fishes, (carotenoids) are commonly added to the diet of salmonid brood fish conditioning, or administering medication to and ornamental “aquarium” fishes to enhance their flesh sick fish. In particular, small ornamental fish farms with an and skin coloration, respectively. The general proportions of assortment of fish require small amounts of various diets various nutrients included in a standard fish diet are given with particular ingredients. It is not cost effective for com- in Table 1. One of the best descriptions of the essential mercial manufacturers to produce very small quantities of nutrients for fish and the nutrient content of various specialized feeds. Most feed mills will only produce custom ingredients is Nutrient Requirements of Fish, a publication formulations in quantities of more than one ton, and by the National Research Council available free on the medicated feeds are usually sold in 50-pound bags. Small Internet at http://www.nap.edu/. fish farmers, hobbyists, and laboratory technicians are, therefore, left with the option of buying large quantities of In their natural environment fish have developed a wide expensive feed, which often goes to waste. Small quantities variety of feeding specializations (behavioral, morphologi- of fish feed can be made quite easily in the laboratory, class- cal, and physiological) to acquire essential nutrients and room, or at home, with common ingredients and simple utilize varied food sources. Based on their primary diet kitchen or laboratory equipment. This paper presents fish are classified as carnivorous (consuming largely animal examples of 1) Experimental and practical fish feed blends material), herbivorous (consuming primarily plant and or formulas that are nutrient balanced and adaptable to par- algae), or omnivorous (having a diet based on both plant ticular conditions; 2) The formulation and preparation of a and animal materials). However, regardless of their feeding semi-purified ornamental African cichlid fish diet that can classification, in captivity fish can be taught to readily be used in the laboratory or when small quantities of feed accept various prepared foods which contain the necessary are needed; 3) The preparation of a gelatin-based diet that nutrients. is often used to administer medicines or other chemicals. Background information on nutrition, feedstuffs, and feed Increased understanding of the nutritional requirements formulations are presented with emphasis primarily on the for various fish species and technological advances in feed feeding of ornamental “aquarium” fishes. manufacturing, have allowed the development and use 1. This document is Cir 97, one of a series of the Fisheries and Aquatic Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date February 2003. Revised March 2009. Reviewed August 2012. Visit the EDIS website at http://edis.ifas.ufl.edu. 2. Juli-Anne B. Royes, doctoral candidate, and Frank A. Chapman, associate professor, Department of Fisheries and Aquatic Sciences, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A&M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Thomas A. Obreza, Interim Dean Figure 1. General amounts of nutrients incorporated into diets for growing fish. of manufactured or artificial diets (formulated feeds) to Carbohydrates. Cooked carbohydrates, from flours of corn, supplement or to replace natural feeds in the aquaculture wheat or other “breakfast” cereals, are relatively inexpensive industry. An abundant supply of feedstuffs are available, sources of energy that may spare protein (which is more and farmers and hobbyists are now able to prepare their expensive) from being used as an energy source. own fish feeds from locally available ingredients. Vitamins and Minerals. The variety and amount of vitamins Proteins and Amino Acids. Fish meal, soybean meal, fish and minerals are so complex that they are usually prepared hydrosylate, skim milk powder, legumes, and wheat gluten synthetically and are available commercially as a balanced are excellent sources of protein. Additionally, the building and pre-measured mixture known as a vitamin or mineral blocks of proteins (free amino acids) such as lysine and premix. This premix is added to the diet in generous methionine are commercially available to supplement the amounts to ensure that adequate levels of vitamins and diet. minerals are supplied to meet dietary requirements. Utilizing raw fish as a main ingredient in fish feeds has long Pigments. A variety of natural and synthetic pigments or been recognized to be harmful to the health and growth carotenoids are available to enhance coloration in the flesh of fish due primarily to the presence of the anti-nutrient, of salmonid fish and the skin of freshwater and marine thiaminase. Thiaminase, an enzyme that destroys thiamine ornamental fish. The pigments most frequently used supply (vitamin B-1), one of the essential water-soluble vitamins, the colors red and yellow. The synthetically produced is mostly found in freshwater fish and is destroyed by heat pigment, astaxanthin (obtained from companies such as (i.e., cooking). Other concerns related to using raw fish in Cyanotech and F. Hoffmann-La Roche Ltd.), is the most diets include the spread of infectious diseases such as myco- commonly used additive (100-400 mg/kg). Cyanobacteria bacterium and botulism. In preparing diets, preferential use (blue-green algae such as Spirulina), dried shrimp meal, of marine fish is suggested to minimize thiaminase activity, shrimp and palm oils, and extracts from marigold, red and raw fish could be steamed or poached. peppers and Phaffia yeast are excellent natural sources of pigments. Lipids. Oils from marine fish, such as menhaden, and vegetable oils from canola, sunflower, and linseed, are Binding Agents. Another important ingredient in fish diets common sources of lipids in fish feeds. is a binding agent to provide stability to the pellet and 2 reduce leaching of nutrients into the water. Beef heart has Other Feedstuffs. Fiber and ash (minerals) are a group of traditionally been used both as a source of protein and as an mixed materials found in most feedstuffs. In experimental effective binder in farm-made feeds. Carbohydrates (starch, diets, fiber is used as a filler, and ash as a source of calcium cellulose, pectin) and various other polysaccharides, such as and phosphorus. In practical diets, both should be no extracts or derivatives from animals (gelatin), plants (gum higher than 8-12% of the formulation. A high fiber and ash arabic, locust bean), and seaweeds (agar, carageenin, and content reduces the digestibility of other ingredients in the other alginates) are also popular binding agents. diet resulting in poor growth of the fish. Preservatives. Preservatives, such as antimicrobials and Other common feedstuffs used in ornamental fish diets antioxidants, are often added to extend the shelf-life of include live, frozen, or dried algae, brine shrimp, rotifers or fish diets and reduce the rancidity of the fats. Vitamin E other zooplankton. The addition of fish or squid meal will is an effective, but expensive, antioxidant that can be used enhance the nutritional value of the diet and increase its ac- in laboratory prepared formulations. Commonly available ceptance by the fish. Fresh leafy or cooked green vegetables commercial antioxidants are butylated hydroxyanisole are often used. Although vegetables are composed mainly (BHA), or butylated hydroxytoluene (BHT), and ethoxy- of water, they contain some ash, carbohydrates, and certain quin. BHA and BHT are added at 0.005% of dry weight vitamins. Kale, dandelion greens, parsley, and turnip greens of the diet or no more than 0.02% of the fat content in the are examples of relatively nutritious vegetables. diet, while ethoxyquin is added at 150 mg/kg of the diet. Sodium and potassium salts of propionic, benzoic or sorbic Feed Formulations acids, are commonly available antimicrobials added at less With few exceptions, feeding a single type of food is neither than 0.1% in the manufacture of fish feeds. complete nor balanced and does not supply all the nutrients Attractants. Other common additives incorporated into a fish might need in its diet.