Basic principles of feeding aquarium fish.
Fish are living organisms, and the food requirement of even fish of the same species is naturally different, not to mention the fact that aquariums usually house fish of different species and ages together. It is known that a fish grows all its life, only at different rates. Accordingly, it feeds. It is necessary to know the approximate food requirement of fish. The amount of food consumed by a fish per day depends on many factors. In natural conditions, with a variety of food and its significant dispersion, the feeding frequency of different fish varies. The daily food intake is different for individual species. In the same species, this diet changes depending on the age of the fish, the quality of the food, the season of the year, the condition of the fish, and the concentration of feeding fish.
Fish differ from each other not only in that they prefer a certain diet (i.e., a specific type of food), but also in their feeding behavior. Carnivorous fish usually set an ambush, stealthily approach their prey, or remain motionless, waiting for a suitable victim to swim by. Other predators, which usually chase their prey, rely mainly on their speed, trying to catch and seize the victim. The amount of food and the frequency of its intake may differ for different fish species, and, furthermore, usually depend on the size of the prey. For example, large carnivorous fish are accustomed to eating a large portion of food all at once – for example, eating a whole fish, and this lasts them for several days.
The other extreme is some herbivorous fish, which spend a lot of time nibbling on algae or snatching small food from the water. Fish of other species can spend many hours feeding on algae and other plant food. The food of herbivorous fish consists of living or decaying plant tissues. Such food is obtained by fish by biting off pieces of plants or picking them up entirely. Some herbivorous fish eat mainly algae. The required amount of food and the frequency of its intake may also depend on the stage of development or reproductive state of the individual, as well as on environmental factors – such as the seasonal availability of certain types of food and water temperature.
The aquarist must take into account another important aspect of fish feeding behavior, namely, what position the fish occupies in the water when feeding. For example, most catfish and loaches feed mainly on the bottom, while some egg-scattering and livebearing toothcarps feed predominantly near the water surface. Between these two extremes are other fish that feed in the water column; these include most popular aquarium species, including almost all barbs, rasboras, and tetras. The position of the fish’s jaws is a useful, although not infallible, sign indicating the water horizon in which it feeds. If the fish’s jaws are directed downwards or are low-set, such a fish usually feeds at the bottom; fish with jaws directed forward feed in the middle water layers, and those with jaws directed upwards feed at the water surface.
Many fish are capable of feeding at any level. However, some (particularly those with downward-oriented jaws) find it difficult to take food at other levels, especially if they are forced to feed at the water surface, as this requires them to adopt a completely unnatural posture. Moreover, fish of some species are generally very reluctant to leave their preferred level. Therefore, far from all bottom-dwelling fish rise to the water surface to take floating food, and some surface-dwelling fish do not want to follow food sinking to the bottom through the entire water column.
Usually, young fish consume relatively more food than adults. At the same time, juveniles at high concentrations feed more intensively than at low ones. In adult fish, on the contrary, the feeding intensity decreases at significant concentrations. The daily food consumption of fish larvae is equal to their mass, i.e., 100%. The amount of food consumed per day also depends on the quality of the food itself. The varying amount of eaten food is directly related to its caloric content and sometimes digestibility.
The intensity of food consumption depends on the condition of the fish. Fatter fish eat less food than poorly nourished ones. During spawning, many fish stop feeding. The food requirement is reflected in the behavior of the fish: intraspecific and interspecific competition for food manifests itself. Growing fish need to be fed frequently and abundantly. In the tropics, fish are distributed more evenly regarding major available foods, and there are more omnivorous (euryphagous) species and food individualists (stenophagous) there compared to temperate ecosystems.
Often in literature, the following recommendation is given as an approximate feeding norm: “Feed the fish enough so that it is completely eaten in about 5 minutes.” However, such a recommendation cannot be applied to all species. This is another variant of averaged calculation that is not applicable in practice. In practice, the duration of a single feeding is established experimentally, and for most lively, active fish, it equals not five, but literally one or two minutes.
And there are such fish (for example, Crenicichla, some brisk barbs) that eat a sufficient amount of food for themselves literally in seconds. There are opposite examples: a number of fish eat very long, slowly, thoroughly, studying the food object for a long time at first. Such fish require 10-15 minutes, and sometimes more, to eat a sufficient amount of food. This does not mean that fish with different feeding types cannot be kept together. They can, but they should be fed specially. It is impossible to establish any standard food consumption norms per fish. The amount of food consumed by a fish depends on many factors.
Possible types of food and feeding frequency depend on the species of fish and, moreover, can be influenced by environmental factors. Most fish species, as well as fry of almost all species, feed continuously in nature, so it is better to feed them small portions several times a day than to give a large portion once a day. When maintaining a community aquarium with many different fish, it is usually recommended to feed them two or three times a day in small portions. The exception is fish that feed on large prey. For example, some predators can eat a whole fish that is only half their size. Such fish need to be fed only two or three times a week, and they may even refuse extra food if offered.
Adult fish should be fed daily, at a specific time, preferably twice a day, but without overfeeding, as obesity leads to infertility. It is unacceptable to feed fish, except for large predatory specimens, only once a day. Whatever food is fed, it should be given in portions while observing their activity. Each portion must be completely eaten. Portion feeding is also necessary during the period when fresh water needs to be given the opportunity to “age” as quickly as possible, avoiding clouding and spoilage.
Having had their fill, fish very soon begin to beg for food again, swimming near the glass. One should not yield to this, as the natural instinct of fish prompts them to constantly search for food. And where else to look for it, if not in the usual place? Having learned to feed fish in portions, the aquarist will understand its advantage over chaotic feeding – the water will not become cloudy. It is best to feed in the same place and at the same hours. Fish accustomed to this quickly gather in a school, and no one is left out. However, a fish that has not had enough this time will not miss out next time.
The aquarium must be closely monitored so that all fish constantly receive their share of food. If there are many fish in the aquarium and the strong ones drive away the weak, there should be several feeding spots. Fish that swim too slowly, as well as timid fish and nocturnal fish, may well miss feeding time. The same applies to individual fish at the bottom of the aquarium hierarchy. If you feed a little every day, the strongest ones will eat. Therefore, 2 times a week, fish are fed to satiety so that the small and weak ones get their share. If there are weak fish in the aquarium that do not dare to take part in the general commotion that arises during feeding, stand modestly aside, and make do with pathetic crumbs, be sure to feed them separately. Specifically slip food right under their noses, otherwise they will soon weaken further and quickly die.
It is not at all necessary to give food only in one specific place, for example, only in a feeding ring. In my opinion, this device is generally superfluous in an aquarium. Healthy, active fish will find food anywhere. Aquarium-kept fish adapt to the feeding regime established by general rules developed through practical experience. To quickly form a school before feeding, fish can be conditioned with a conditioned reflex to a gentle tap of a finger on the glass.
Aquarium fish feeding regime. Feeding frequency.
Correct and balanced nutrition. Macroelements, Microelements, Vitamins. 
