Aquarium with livebearing fish.
Continuation…
Plants are necessary in an aquarium with livebearing fish. Most of the time, the fish stay in the middle and upper water layers. Due to the fact that many species of livebearing fish are found not only in fresh but also in brackish waters, it is necessary to figure out which species belong to fresh, brackish, and marine waters. Fry of livebearing fish willingly hide in thickets of fine-leaved Javan moss (Vesicularia dubyana).
It is very useful to have it in the spawning aquarium, because the newborn fry first “fall” to the bottom and hide in the moss, and only after a short period of time rise to the water surface, where they hide among plants floating near the surface and in the water column. Among the plants most suitable for use in aquariums with livebearing fish is the Amazon sword plant (Echinodorus paniculatus); it successfully grows and develops in water with a wide range of pH and hardness. Place the Java fern (Microsorium pteropus) in the brackish water of livebearing fish aquariums.
Thickets of floating plants such as Riccia, Pistia, Salvinia, and the floating form of the water fern Ceratopteris are an excellent refuge for fry; in these thickets, they find infusoria and other small food in the first days of their life. For decoration, you can use various species of Cabomba, Hygrophila, Limnophila, Myriophyllum, Najas, as well as Egeria densa, Echinodorus, bladderworts (small and humped), and Salvinia. For aquariums with a water salinity exceeding 1-2%, the use of some charophyte species, such as Chara fragilis, and Cryptocoryne ciliata is most likely. Both of these plants are known in natural brackish waters.
The intestine in livebearing aquarium fish is quite long compared to body size. Therefore, most are omnivorous, with a tendency to vegetarianism, and extract maximum nutrients from plant food. Fish are constantly busy scraping the slightest algae plaque and dirt from plant leaves, keeping them in perfect cleanliness. To combat filamentous algae, you can use Limia, platies, and mollies. An annoying exception is representatives of the Goodeidae family, which often damage plants, especially delicate ones.
Livebearers in nature feed on a variety of foods, but mostly plant-based. Poeciliids feed mainly on insects and their larvae. To one degree or another, most species also feed on plant food, primarily algae. Some species, for example, mosquitofish and guppies, prefer mosquito larvae in nature. Platies, swordtails, and especially mollies are more herbivorous fish. And if there is little or no plant food in their diet, they waste away and die rather quickly from intestinal disorders.
In the aquarium, however, these fish are always cleaning and gathering something, and can do this very effectively: an aquarium with platies or mollies usually looks very neat and clean. But Belonesox, a kind of “livebearing pike,” has a pike-like disposition. And a feeding method: they gladly snack on other livebearers, and in general eat everything that moves and can fit into their mouth. They need to be kept separately or with large fish.
An important condition for the successful keeping and reproduction of livebearers is a varied and complete diet. Livebearers should be fed live foods and mandatory plant foods. This is another mistake of novice aquarists – feeding only live food. Without plant component supplements, fish get sick. As plant food, you can use Wolffia, scalded and chopped lettuce leaves, dandelion, etc. Fish willingly eat bloodworms, corethra, tubifex.
Correct food dosage along with a sensible alternation of feed organisms is of great importance. Overfeeding fish, in addition to known negative factors, leads to a violation of the linear-weight balance, and underfeeding leads to the appearance of undersized, stunted individuals that bring no joy to aquarists. With improper feeding, the scales of males swell, and they die. Females are constitutionally stronger and less susceptible to diseases.
The most interesting and characteristic feature of this group of fish is livebearing. Representatives of the family are characterized by pronounced sexual dimorphism. In most species, females are larger and males are smaller; the latter are colored significantly brighter and have elongated caudal and dorsal fins. In pregnant females, a dark spot is noticeable in front of the anal fin. Thanks to livebearing, poeciliids gain many advantages both in nature and in the aquarium.
Their fry are much more viable than ordinary fish fry, larger and more active. And they grow faster, usually fully maturing for reproduction in three to four, rarely five to six months (in some species of Goodeids and Mollies). The absence of difficulties in feeding the babies makes them an easy object for breeding, and often the aquariums of beginner enthusiasts are filled to the limit with the offspring of one or two pairs. The female can store sperm in her body, so a single mating can give life to several generations of fry.
The average size of a generation varies – it depends on the species, as well as the age and size of the female, and can range from two or three to 200 or more fry. Depending on the species and external conditions, the development of fry until the moment of “birth” lasts from 7-15 days to 2-2.5 months. These fish give birth to live fry capable of swimming and feeding immediately, and therefore parents do not need to care for them. Some species crossbreed well with each other.
Fresh water in many species stimulates the release of fry. Most species can be bred in a not very densely populated aquarium with floating and fine-leaved plants. By reproduction type, the only exception in the family is Tomeurus (Tomeurus gracilis), which spawns eggs like most fish. Therefore, its systematic position is not entirely clear, as, indeed, for a number of other livebearers.
In all livebearing fish, in accordance with their method of reproduction, fertilization is internal, like in reptiles, mammals, and birds. Accordingly, special adaptations have arisen for this, analogous to the reproductive organs of mammals. In males, this is a modification of the anal fin called the gonopodium, and in females, a brood pouch analogous to the uterus. In young males, the anal fin over time, by the period of puberty, begins to lengthen and turn into a gonopodium, which they use to fertilize females. The gonopodium of males is formed by elongated front rays of the anal fin, forming a hollow tube.
Due to the presence of a tube-shaped gonopodium in mature males, it is very easy to differentiate the sexes in these fish. Only livebearing toothcarps and halfbeaks (belonging to a separate family) possess this organ. It is precisely this that is the distinguishing feature of male livebearing fish, rather than coloration, body shape, or fin shape. In females, the anal fin is exactly the same as in other fish: triangular or rounded, formed by a large number of rays.
Some “advanced” aquarists determine the sex of fish by size, saying that the larger one must be a female, and the smaller one a male. Again, this is not entirely true. All else being equal, livebearing females are slightly larger and much fuller than their suitors. However, swordtails and platies have an interesting feature – some males mature early, at three to four months, while others “sit” for up to half a year or even more. These “late” fish grow to very large sizes, often larger than females. And since their sex is finally determined significantly later than that of the “early” ones, they are often mistaken for females.
To avoid mistakes, one should look at the formation of the gonopodium (in a three-month-old “late” male, it usually already begins to form little by little) and, most importantly, at the presence of a spot at the base of the anal fin. There the fish’s skin is transparent, and the edge of the brood pouch is visible. However, it is not always easy to see, especially in red and black forms.
The main differences between Poeciliids and Goodeids boil down mainly to the method of carrying offspring and the structure of the gonopodium. In Goodeids, it is short, thick, and usually called an andropodium. Only the first few rays of the fin are converted into a copulatory organ, while the rest look completely normal. Therefore, a beginner may find it difficult to determine the sex of such fish as Xenotoca at first glance. There are also differences in carrying fry: in Poeciliids, eggs develop for about 15 days (sometimes more) at the expense of yolk reserves, and fry enter the water, directly hatching from eggs at the moment of birth.
Poeciliid fry are much smaller than their parents, but develop quickly, reaching sexual maturity in just a few months. In Goodeids, fry are much larger. In the red-tailed xenotoca, a female 8-9 cm long gives birth to about 20 fry, each a centimeter long. Fry develop slowly, becoming adults at best by six months. And Goodeids carry them twice as long as their small relatives.
In addition, their fry feed in the mother’s womb not on the yolk of their own egg, but directly at the expense of the mother’s circulatory network, connecting to the wall of the brood chamber with a special thread – trophotenia, an analogue of the umbilical cord in mammals. Since Goodeids feed their babies in such an unusual way for fish, it is very important to provide the pregnant female with a complete diet and reduce stress as much as possible, as females may abort their fry.
Fish from the Poeciliidae family have long been the focus of breeders and geneticists. Rapidly multiplying, with a large number of color forms and variations in nature, unpretentious, they also crossbreed perfectly with each other. Of course, not all with all, but guppies easily crossbreed with micropoecilia and mosquitofish, platies with swordtails and limias, and molly species with each other. In fact, the entire assortment of selective livebearers today is represented by four genera: guppy, platy, swordtail, molly. Why is that? After all, there are several species of swordtails, platies, and mollies in nature?
It’s simple: over the past century and a half, the species of these genera have been so frequently and intensively crossbred by breeders and just amateur aquarists that species differences have been almost completely lost. As for the division of platies, swordtails, and mollies into separate species given on some websites and in reference books to which a particular form belongs… In my opinion, such reasoning is, to say the least, not entirely legitimate. The primary genes of the parent species have mixed so long and firmly that you can no longer trace back to the ancestral form.
A common problem encountered when keeping these fish is uncontrolled reproduction. It is worth adding neighbors to the “livebearers,” for example, labyrinth fish (honey gouramis and gouramis), angelfish (it should be remembered that angelfish are more thermophilic), you can add some species of peaceful South American cichlids, for example, apistogrammas. Thus, your population will be regulated naturally, and these species will eat excess fry. It is also quite possible to introduce a few cleaner catfish into the aquarium, such as Ancistrus.
Keeping Guppies (Poecilia reticulata).
Aquarium with livebearing fish. 
