Tropical fish are fish found in aquatic tropical environments around the world. Fishkeepers often keep tropical fish in freshwater and saltwater aquariums. The term "tropical fish" is not a taxonomic group, but rather is a general term for fish found in such environments, particularly those kept in aquariums.
The term coldwater fish can have different meanings in different contexts.
A freshwater aquarium is a receptacle that holds one or more freshwater aquatic organisms for decorative, pet-keeping, or research purposes. Modern aquariums are most often made from transparent glass or acrylic glass. Typical inhabitants include fish, plants, amphibians, and invertebrates, such as snails and crustaceans.
Freshwater fish may be either coldwater or tropical species. Although freshwater aquariums can be set up as community tanks, coldwater and tropical fish are generally not mixed due to incompatibilities in temperature requirements. Coldwater aquariums house goldfish and other species that do not require a heating apparatus. Warmer temperatures would actually increase their metabolism and shorten their lifespan. For a tropical fish tank, maintaining a warm environmental temperature ranging between 75 and 86 °F (24 and 30 °C) enables different tropical fish to thrive at different temperatures.
The guppy (Poecilia reticulata), also known as the millionfish or rainbow fish, is a member of the family Poeciliidae and, akin to most New World members of the family, is considered a livebearer. Male guppies, which are smaller than females, have ornamental caudal and dorsal fins. Wild guppies generally feed on a variety of food sources, including benthic algae and the larvae of aquatic insects.
Originating from northeast South America, it has been introduced to many environments and are now found all over the world; guppies are now one of the world's most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. They are highly adaptable and thrive in many different environmental and ecological conditions. Guppies are used as a model organism in the fields of ecology, evolution, and behavioural studies.
The zebrafish (Danio rerio) is a species of freshwater ray-finned fish belonging to the family Danionidae of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often called a "tropical fish" although it is both tropical and subtropical).
The zebrafish is an important and widely used vertebrate model organism in scientific research, particularly developmental biology, but also gene function, oncology, teratology, and drug development, in particular pre-clinical development, due to its scalability from high numbers of offspring and ease of drug delivery through water into the gills. It is also notable for its regenerative abilities, and has been modified by researchers to produce many transgenic strains.
The ocean sunfish (Mola mola), also known as the common mola, is one of the largest bony fish in the world. It is the type species of the genus Mola, and one of five extant species in the family Molidae. It was formerly misidentified as the heaviest bony fish, which is actually a different and closely related species of sunfish, Mola alexandrini. Adults typically weigh between 247 and 1,000 kg (545 and 2,205 lb). It is native to tropical and temperate waters around the world. It resembles a fish head without a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long (about 5.9 ft) when their dorsal and ventral fins are extended.
Many areas of sunfish biology remain poorly understood, including mating practices and spawning locations, early life stages, movement and migration patterns, population structure and status, diet and trophic ecology, and post-release survival rates, and various research efforts are underway, including aerial surveys of populations, satellite surveillance using pop-off satellite tags, genetic analysis of tissue samples, and collection of amateur sighting data.