Surely, you will remember for a long time a phenomenal view of a large number of fish shining with reflected light, swimming in tight clusters and making circles. This unforgettable image is created by schooling fish. They do not have to learn it at all – swimming in shoals is written in their genes.
A shoal can be formed by a few to even a million fish, but the most common are shoals consisting of a few hundred or a few thousand specimens – mainly within the same species. Usually these are fish of small size and impressive reproductive abilities, and what is more, they gain weight very quickly. It is a form of effective strategy – such behaviour protects them from predators, allows more efficient food acquisition and improves swimming efficiency. It is also no secret that a single fish in a shoal encounters less water resistance, which significantly reduces the effort and makes the shoal go faster if necessary. Frightened fish tighten ranks, move faster and regularly change their position, which confuses the attacker.
In a shoal there is no permanent leader. Individuals who are at the head of the shoal after making a change of direction take the lead. Here are some of the most popular representatives of this kind of fish.
Neon Innes (Paracheirodon innesi)
The Neon Innesa is a species of freshwater fish in the bryozoan family that lives in the western and northern Amazon basin and eastern Peru. It is also sometimes called Neon or Innes’s bullhead. It inhabits forest streams, abundant in tree branches, submerged branches and leaves. It reaches the length of 1-5 cm. It is a peaceful schooling fish, which means that you should keep more of them in an aquarium. In a large group they feel much safer, are more active and simply look nicer.
Innesa is very sensitive to changes of water parameters and temperature. It feels best in soft water with temperature 22-25 C. It accepts both dry and frozen food.
Gobies (Gymnocorymbus ternetzi)
Gymnocorymbus ternetzi, also known as black tetra, is a freshwater fish of the biting family. In the wild it can be found in the waters of Brazil, Bolivia and Paraguay. It inhabits mostly slow-moving rivers and ponds. It lives in a herd, growing up to 8 cm long.
If we want to keep it in perfect condition, we should keep it in a larger group. It needs a large aquarium (from 100 liters of capacity) with space for free swimming. Tank should be densely overgrown, with dark bottom (in too light it loses color). Floating plants are advisable in this case to reduce too bright light. This species requires temperature between 22-26°C – in lower temperature it becomes skittish and loses its coloration.
Black Tetra is quite resistant to changes of water parameters. It is easy in breeding and recommended also for beginners. It feeds on various kinds of food but it is advisable to regularly feed it with live or frozen meat food.
Denison’s Barbel (Puntius denisonii)
The Denison’s Barbel is an endemic species that is stationed in rivers, streams and creeks in the southern parts of India where there is dense vegetation and the bottom is rocky or sandy. It belongs to the group of herd fish and very dynamically moving. It grows up to 15 cm.
In order to expose the natural beauty of these creatures, it is necessary to create suitable breeding conditions for them. Denison’s barbs therefore require a large aquarium with plenty of swimming space and dense vegetation. The substrate should be made of sand or fine gravel and the water should be clean and well-oxygenated with a slightly acidic to slightly alkaline pH.
There are no major problems with their feeding. They readily eat both live and frozen food as well as artificial food, however their diet should be varied.
Rockfish (Pterophyllum scalare)
Scalar is a freshwater fish from the cichlid family. The common name sailfish comes from the characteristic shape of its dorsal and anal fins (another name is moonfish – editorial added). In the wild it can be found in numerous river systems. It occurs in groups in the upper and middle reaches of the Amazon River, together with all its tributaries. It lives in swamps and floodplains among dense vegetation. The strongly flattened shape of its body enables the scarer to drift freely among bushes and escape from predators. It is a herd fish, rather peacefully disposed. It is also very intelligent – in threatening situations its representatives can skillfully cooperate with each other. In breeding conditions they live about 15 years, reaching body length of 15 cm and height of up to 35 cm. They are voracious and omnivorous, but prefer live, frozen or dried meat food. They also eat the fry of other fish.
Rockfish are one of the most characteristic and dignified fish kept by aquarists. They gained popularity probably thanks to their unusual structure (the body is narrow and high, resembling a disk). They are relatively large fish, therefore they require a large and high tank (at least 200 l and at least 50 cm high). The aquarium should be planted with large plants so that the fish can move freely among them, and the optimal water temperature should oscillate between 24-28°C (in temperatures below 20°C adult scalars get sick). A sandy bottom with some leaves, decorated with roots and branches is most suitable for them. Filtration should be strong and the water clean and regularly changed.
A school of fish swimming in an aquarium strongly affects its attractiveness and gives it a natural look. So it is worth considering buying more fish of the same species.
Featured photo: Wikipedia