Freshwater Fish

Freshwater fish are those that life their whole life or a major part of their life in freshwater like rivers and lakes where the salinity present in the water is less than 0.05%. To survive in the freshwater, fish need a huge range of physiological adaptations to help keep the ion concentration in their body balanced. Of all the known fish, 41% are found in freshwater and the primary reason for this is the fact that due to the rapid speciation the scattered habitats make possible.

If you are looking for fish for your aquarium then select bright and lively fish. I guess the easiest choice is the goldfish if you are looking for a small aquarium. But if you are considering a large aquarium then you must have a fair idea about the various families of fish that are available. In this article, I will be covering the characteristics of some of the common freshwater fish families that are suitable for the aquarium.

Anabantidae

The fish belonging to this family are native to the waters of Asia and Africa and are also known as the 'labyrinth' fish as they have an organ in their head which helps them breathe air if necessary. Further, the fish that originate from Asia have their ventral fins modified which helps them sense food. These fins protrude in front of the body of the fish so as to help them detect food in the dark waters of their natural habitat. Many species of fish belonging to this family also produce a characteristic floating bubble nests.

Callichthyidae

The catfish belongs to this family and are widely distributed in North and South America, Europe, Africa and Asia. These fish can survive in near stagnant water and also have the ability to breathe atmospheric air. Some members of this family have a strong suckered mouth with the help of which they can cling to stones. Various egg laying methods are adopted by this family.

Characidae

This family comprises one of the largest freshwater fish families in the world although the largest number of representatives is from South America. The members of this family are characterized by the presence of either teeth or an adipose fin and in some cases both.

Cichlidae

This family consists of carnivorous fish that are found in Asia, Africa, Central and South America. This family is considered to be highly evolved as they exhibit a high degree of parental protection including mouth brooding. Many species of this family make excellent inhabitants for the aquarium despite their aggressive reputation.

Cyprinodontidae

This family of fish is commonly found in Asia, Africa and Southern Europe and the fish belonging to this family include tooth-carps (also known as killifish) who prefer slightly acidic water and dimly lit conditions. The mouths of these fish are armed with teeth which help them actively hunt down smaller species. Eggs are either laid on the roots of floating plants (egg hangers) or buried under the clumps of peat or other equally suitable substrate matter (egg-buriers).

Gasteropelecidea

This family of fish is found in South America and is characterized by bodies that resemble a hatchet. They also have upward inclined pectoral fins that help the fish glide when they jump out of the water and fly a short distance to escape danger.

Poeciliidae

This is a small family of fish that originates from the Southern part of North America, Central America and the northern part of South America. Some of the common fish that belong to this family are the guppies, swordtails and mollies. The anal fin of the male fish forms the sexual organ which is known as 'gonopodium'. Sperms are introduced into the female fish from these organs. Live young are produced and these are capable of swimming and feeding themselves a few minutes after they are born.

Scatophagidae

These are brackish water fish that are found in the river mouth, estuaries and the coasts of south-east Asia and northern Australia. The fish belonging to this family have a deep, laterally compressed body, two dorsal fins and they feed by scavenging on plant and animal matter.

Toxotidae

The members of this family are also known as 'archer' fish because of their unique method of squirting jets of water at insects that sit on the overhanging foliage to knock them into the water. These fish are found in the coastal waters of India, the Persian Gulf, Australia and Indonesia.