Vitamins, Minerals, and Trace Elements in Fish Feed.
Dry foods for selective fish forms cannot completely replace live food. All these substitutes for live foods are deficient in their composition. Using them for a more or less extended period is not recommended. It should be remembered that their shelf life does not exceed 4 months. Every time the package is opened, light and air enter the food. As a result, even in good food, vitamins and nutrients, such as fatty acids, are destroyed. Therefore, the package should be used up within two, maximum three months, so that light and air do not decompose the valuable nutrients of the feed. Food must be purchased in such a quantity (package size) that it can be fully consumed within a maximum of 3 months after opening.
After this period, feeding fish with this food is no longer acceptable: it accumulates fat oxidation products, indicated by a stale, “rancid” odor, partially degraded proteins, and 
other harmful components, while virtually no vitamins remain by this point. It is no coincidence that all dry food manufacturing companies pack their products in such diverse packages: from a 10-gram sachet or 25 mm jar to a huge 10 or 15-liter plastic bucket. Therefore, it is better to buy small packages; furthermore, this provides the opportunity to vary different feeds more often, preferably from different brands. The imaginary “economy” of buying food in larger containers usually leads to financial losses: from discarded spoiled food to sick or even dead fish caused by feeding them stale food. The same (or even worse!) can be said about purchasing dry foods “by weight” without packaging.
High-quality dry fish foods must be packaged in hermetically sealed containers to prevent spoilage during storage. When purchasing food, pay attention to product quality and do not be tempted by poorly packaged products or products in transparent packaging of unknown origin. Pay attention to the packaging — never buy expired food. Such food can no longer contain a sufficient amount of vitamins and nutrients, or they are of low quality, or have already decomposed due to light and air.
The next thing to remember is the proper storage of dry food. First of all, when opening a jar of food, check if it is hermetically sealed with plastic or foil, and often also vacuumed or filled with an inert gas environment (nitrogen). In addition, since some vitamins, such as vitamin C, can be destroyed by heat, moisture, and light, feeds should be stored in a cool, dry place, and the jars must be opaque with tightly fitting lids. Dry food must be genuinely dry, not clumped together.
The jar of food must be tightly closed with a lid immediately after each feeding to minimize the contact of the food with moisture and atmospheric oxygen. The food should be stored in a dry place at a temperature not exceeding 25°C, or preferably even lower, from 5 to 15°C, and under no circumstances in direct sunlight. Very often in the apartments of amateur aquarists, you can see a jar of food standing constantly on the aquarium hood, right on the light fixture. This must never be allowed! Heated by the aquarium lamps and exposed to moisture from the aquarium, the food will quickly become useless and, instead of health, will only harm your fish.
If the food has become damp, caked, or even if it looks completely normal outwardly but has acquired a stale, rancid fat odor — immediately throw it away and do not even think about feeding it to your fish! Fat oxidation products are extremely harmful; they disrupt cell division processes in the organism, which ultimately leads to the development of cancer.
Feeding should preferably be carried out in accordance with the natural needs of the species, giving preference to complete, balanced feeds that include a full complex of vitamins and trace elements. Bad and inappropriate food easily leads to stomach and intestinal diseases. If the food is too fatty, it can lead to intestinal obesity. If the food is too monotonous and poor in vitamins, it can cause general weakening and liver degeneration. A little fasting will not hurt fish. It is just like with humans: it is better to be hungry and vigorous than full and lethargic.
A lack of nutrients supplied with food (proteins, fats, carbohydrates, minerals, and vitamins) leads to corresponding pathologies in fish. Therefore, whenever possible, feeds balanced in major nutrients should be used. One should not forget about the possible poor quality of the feed. This is especially true for feeds or their components containing large amounts of fats. Improper storage of such feed leads to fat oxidation with the formation of highly toxic free fatty acids and peroxides. Using such feeds can lead to the development of pathological processes and the death of fish. Nutrients that supply the fish organism with energy and “building blocks” are proteins, fats, carbohydrates, minerals, and vitamins.
Spirulina is one of the best sources of proteins, essential and non-essential amino acids, minerals, vitamins, and chlorophyll. It contains phycocyanin and other biologically active 
substances. Spirulina is a blue-green filamentous microalga whose cellular structure is characterized by cells located along a spiral filament reaching up to 1 mm in length. The productivity of Spirulina is such that it contains 20 times more protein than soybeans, 40 times more than corn, and 400 times more than beef.
Thus, it is recognized as a superfood also because its nutritional components are more concentrated than in other foods, plants, grains, and grasses. Moreover, digesting Spirulina proteins requires much less energy than digesting traditional foods. It is considered a great aid for hematopoiesis and contains a whole vitamin complex in itself.
There are few vitamins in Tubifex (A1, B1, and provitamin D in trace amounts). This is a very nutritious, high-protein feed that accelerates fish growth. However, Tubifex is severely damaged by freezing: ice crystals destroy the delicate tissues of the soft worms. As a result, a large amount of nutrients is lost, and the food turns into “mush”. Tubifex is one of the most dangerous foods in terms of microflora and chemical toxins. Bloodworms are especially rich in the trace element cobalt. Artemia contains up to 7.2 mcg of vitamin B2 per 1 g.
The most biochemically complete are lower crustaceans: branchiopods (Cladocera), copepods (Copepoda), and fairy shrimp (Euphyllopoda). High protein content in their bodies is combined with a large amount of biogenic elements (calcium, phosphorus, iron, etc.) and a rich vitamin set. Daphnia is one of the most nutritionally complete aquarium feeds. High protein content, numerous trace elements and vitamins, and optimal amino acid composition of the protein make Daphnia a very popular aquarium fish food among aquarists worldwide. They are found everywhere (except for salt-loving Artemia) during the warm season and are especially abundant in temporary and stagnant water bodies. Some species of Daphnia are specially cultivated in fish farms as a highly valuable feed for fish fry.
Plankton contains an especially high proportion of natural plant and animal plankton. These are gently processed, vitamin-rich treats for bottom-dwelling fish, and also serve as an excellent supplement for fry.
Wolffia is an excellent plant-based food for aquarium fish. Its tissues contain 60% carbohydrates, 20% fats, 10% proteins, and vitamins A, B6, C, PP. When cultivated at home, this plant must be kept isolated from fish, for whom it is a great delicacy.
Spinach and nettles contain minerals and trace elements that boost the vitality of your fish and help build their immune defenses. Some authors recommend scalding the leaves, but fish gladly eat fresh leaves as well; however, nettles must be scalded, and should not be omitted as they are a very valuable vitamin component.
Note that both carnivores and herbivores do not shy away from consuming small amounts of plant and animal food. Carnivores need vegetation as a source of vitamins, while animal supplements in the form of plankton and insect larvae are needed by herbivores to replenish essential proteins and amino acids. The need for a particular ratio of plant and animal diet varies depending on the age of the fish and the intensity of reproductive cycles, which in turn determine the seasonality of breeding.
Ready-made frozen foods must be stored in the freezer at –15°C and below, and accidental thawing must be prevented. The value and shelf life of frozen food largely depend on compliance with freezing and storage technology. The faster the cooling and the lower the temperature at which they are frozen, the more completely nutrients and vitamins are preserved. It is especially important to prevent thawing during storage. Properly prepared frozen foods can be stored without loss of quality for 3–5 years.
Let us consider seafood as a feed base. They are convenient, affordable, and nutritious. Squid, scallop meat, red fish, shrimp (preferably simply frozen), mussels, and marine fish roe. Everything except roe, perhaps, can be made into a mash that is easily frozen and then fed. Naturally, depending on the size of the fish, the size of the mash particles can be varied. When thawing, you can add the water-soluble vitamin Fishtamin from Sera.
The growth rate and immunity of fish can be enhanced by introducing cobalt chloride (0.02 – 0.09 mg/kg or 12 mg/L), zinc sulfate (0.05 – 0.5 mg/L — especially during the development of embryos and larvae), iron salts (0.1 mg/L), phosphorus (5 mg/L), ground red pepper (paprika) (15 mg/g), soybean or bean oil (8 mg/g), and UV-irradiated mycelium of the mushroom Lentinula edodes (shiitake) (8 mg/L) into the feed or water. Per 100 g of nutrient mixture, there may be vitamins (mg): C and K 0.5-1.5; B2, B6, B9, and E 1-3; B3 5-15; B4 80-200; B5 4-5; B8 30-40; B12 0.002; H 0.1-0.2. Vitamin A concentrate (fish oil) is added to compound feed at 2% by weight, hydrolyzed yeast at 3%, lake silt (protein-mineral supplement) up to 15%, and sunflower oil lecithin (sediment) at 5-10%.
Purified biomycin sharply activates intestinal microflora at 50 mg per 1 kg of feed. To maintain the calcium-phosphorus ratio, pulverized calcium glycerophosphate (1 tablet per 200 g) or bone meal is added to the prepared food. Do not prepare too much food at once (a 1-2 month supply is sufficient). Store it in the refrigerator in an enameled tray or wrapped in dense paper. Otherwise, under the influence of high temperature, atmospheric oxygen, and sunlight, fats in the compound feed will oxidize into peroxides, which destroy vitamins A, D, and E and have a toxic effect on fish. As antioxidants, ascorbic acid (in the form of ascorbyl-2-phosphate, which remains stable in water for 1-2 weeks), ionol, butylated hydroxyanisole, ethoxyquin, and vitamin E are added to the “food” at 8-12 mg/kg.
Gel-based compound feeds using gelatin (2%), technical albumin (6%), and agar-agar (8% of the feed volume) have recently attracted special interest. They allow introducing any components into the food mixture, including vitamins, hormones, amino acids, biostimulants, adaptogens, tranquilizers, pigments, medicines, etc. Equally important advantages include low water solubility and ease of shaping (shavings, crumbs, pouring into molds for artificial rearing of Symphysodon (discus), spraying into coral polyp cavities, etc.). The only difficulty lies in the varying degrees of acclimation of aquatic organisms to them.
The food preparation process itself is very simple. Gelatin is dissolved in water at 60°C (agar-agar needs to be boiled), after which the remaining components, previously ground in a blender, are added with constant stirring. The resulting homogeneous mass is cooled and placed in the freezer compartment of a refrigerator for storage (temperature not exceeding 18°C). In case of allergies, one should avoid using dry Daphnia and Gammarus for feeding fish (respiratory allergens), as well as handling bloodworms and Tubifex with bare hands (skin allergens). Since only a clean aquarium meets the aesthetic requirements of fishkeeping, monitoring the consumption of compound feeds is of paramount importance.
Preparations for enriching water with vitamins and trace elements.
Minerals and trace elements required by fish. 
