A Complete Guide to Freshwater Aquarium Fish Species and Common Varieties

Freshwater aquarium fish are fish kept in freshwater environments primarily for ornamental purposes, and they are the largest category in home aquariums. Based on their adaptability to water temperature, they are usually divided into two main groups: tropical fish and cold-water fish. Tropical fish require relatively stable water temperatures and are mostly kept in indoor aquariums; cold-water fish are more adaptable and are suitable both for ordinary fish tanks and for garden ponds.

The variety of common freshwater aquarium fish is extremely rich. Among cold-water fish, goldfish and koi are the most representative, with a long history of keeping and a wide range of color patterns and body shapes. Among tropical fish, small species such as guppies, neon tetras and cardinal tetras are brightly colored and easy to keep, making them suitable for beginners; angelfish, discus, oscars and flowerhorns are elegant in form or distinctive in personality and are much loved by more advanced hobbyists; bettas and gouramis have accessory breathing organs and tolerate low-oxygen environments relatively well; there are also bottom-dwelling species such as corydoras catfish and plecos, as well as large and valuable fish such as arowanas.

When keeping freshwater aquarium fish, the key lies in water quality, water temperature and sensible mixing of species. A new tank generally needs to be cycled first, removing residual chlorine from the water and establishing a stable nitrifying system before fish are added; most tropical fish need a heater to keep the water temperature constant. When mixing species, body size and temperament differences should be considered to avoid fights between aggressive species and peaceful ones in the same tank, and feeding is best done in small amounts several times rather than all at once, to prevent leftover food from fouling the water.

Keeping aquarium fish beautifies the home environment and also helps people relax, making it a leisure hobby suitable for all ages. One reminder: never release aquarium fish into wild waters at will, as escaped non-native species may crowd out the living space of native fish, and protecting native freshwater fish resources is also the responsibility of every hobbyist.