Viviparous fish – intriguing and beautiful

Aquaristics/Recreational activities
Chandler Lee
Viviparous fish – intriguing and beautiful
It takes approx. 5 minutes to read this article

Livebearing fish are undoubtedly the most popular tropical fish and are most often chosen by beginner aquarists. They are easy to keep, do not have excessively high requirements as to water quality and are by nature very peaceful, sociable and constantly active. In short – they are perfect for stocking into any type of aquarium.

Live-bearing aquarium fish are fish species whose females store fertilized eggs inside their bodies – this is where the entire embryonic development takes place until hatching. As a result, the young fish are born fully formed. Males of viviparous species have an anal fin transformed into a copulatory organ called gonopodium, through which they introduce the sperm into the anal-genital opening of the female.

There are many species of livebearing fish available in aquarium stores, and the most popular are guppies, swordtails, mollies and platies.

The guppy (Peacock guppy – Poecilia reticulata)

In the wild the peacock guppy inhabits South America north of the Amazon River. Most likely through breeding, the guppies have also spread to other continents, including Asia and Europe. They are mostly stationed in slow-moving or standing water with abundant vegetation, such as rivers, ponds, canals or ditches. Interestingly, they are found even in heavily polluted bodies of water. They usually stay near the surface of the water. They feed on a variety of food, depending on the environment they occupy – most often it is small zooplankton or algae.

Over the years the guppy has become one of the most common live-bearing fish kept by aquarists. In home tanks, however, there are mainly specimens belonging to ornamental forms, i.e. much more colourful ones. Currently there are 12 standard types of guppies, based on the shape of their tail fin: fan, veil, pennant, flame, triangular, blade, needle, two-bladed, rocket, lyre, upper sword and lower sword.

This fish does not require a large aquarium, but the minimum recommended tank size is about 25 liters. Optimal water temperature is 20-23°C, although race varieties are more sensitive and require higher temperature (even up to 27°C). The water should also contain small amounts of rock or aquarium salt, which kills protozoa and regulates the fish’s metabolism.

The guppy is an omnivorous fish. It readily eats any type of food, but must be fed a varied diet. For proper development it also requires plant food (e.g. algae).

Heller’s gladiolus (Xiphophorus hellerii)

The Heller’s Swordtail, otherwise known as the Green Swordtail, belongs to the freshwater fish of the family of Beauties, and its natural habitat is the waters of Southern Mexico, Honduras, and Guatemala. In the wild it is characterized by a gray-green, shiny color with a thin maroon stripe running along the lateral line, while in culture there are many different colored varieties. The most popular are the red and orange varieties, but there are also black, Berlin, wagtail, pineapple, kohaku varieties, obtained by selection and cross-breeding with the spotted hare. The male is more slender than the female and its tail resembles a sword (hence the name).

This kind of fish requires bigger aquarium of at least 100 liters with clean water, because in small tanks it dwarfs and doesn’t develop properly. Therefore, good filtration is needed, as well as weekly water changes (about 10-20% of capacity). The tank should be well lit and planted with vegetation (e.g. cabomba, rotala, nurzanus or frogweed), with sufficient swimming space. The optimal temperature is 24-28°C. It is also worth ensuring that there are 2-3 females per one male, as they are aggressive towards other males of the same species.

Swordtails accept live, frozen and dry food, and their diet should be additionally enriched with plant foods.


Molinesia is another genus of freshwater fish from the family of Beautidae. In natural conditions they inhabit fresh and brackish water areas of Central America – from Mexico to Colombia. However, their appearance today is significantly different from their original, wild forms. Over hundreds of years, many color variations have developed as a result of species mixing and interference by various breeders. The most common species that dominate aquariums are the Sphagnum Molinesia (Poecilia sphenops), the Wide-finned Molinesia (Poecilia latipinna), and its variant, the Black Molly. Some species also do well in marine aquariums.

A tank for Molinesia should be spacious and overgrown with dense vegetation, with enough space for swimming. It is also worth taking care of good filtration, regular water changes and strong lighting. The water should have a stable temperature of 24-28°C and be slightly salty, therefore rock or sea salt should be added (1 teaspoon per 10 l of water).

Spotted clownfish (Xiphophorus maculatus)

The spotted platypus, also belonging to the family of beauties, is naturally found in rivers, ponds, and floodplains in Mexico, Honduras, and Guatemala. Females grow up to 7-8 cm in length, while males barely reach 6 cm. Individuals in the wild are olive in color, with a blue sheen. In breeders many varieties were created with interesting, intriguing and even funny names (Mickey Mouse, wagtail, comet, salt and pepper, mouse or golden), various colors (orange, red, black and red, blue etc.) and types of fins.

The platka does not require a very large tank – 7 liters per adult is enough. The aquarium should have dense vegetation and quite a lot of free space for swimming, as well as very good lighting. It is advisable to choose hard water with neutral pH (6.5-8.0) when keeping these fish.

This species leaves a lot of freedom in terms of food. Spotted dogfish feed on live, frozen and dry food with a variety of lettuce leaves, plant food or algae.

Keeping live-bearing fish can provide many pleasurable experiences. They have striking, vivid colors, which are often the result of many years of breeding selection. Most species are peaceful and gentle, so they can be kept in both single and multi-species aquariums, enriched with interesting arrangements and lush vegetation.

Featured photo: Pixabay

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