Nothobranchius rachovii

Aquarium fish: Nothobranchius rachovii (Nothobranchius rachovii)
Size: 5.5 cm
Origin: Africa
Water temperature: 21-26 ° C
Aquarium volume: 40 l

Nothobranchius rachovii (Nothobranchius rachovii ) – a small, beautifully colored, short-lived aquarium fish from the  Nothobranchiidae family . It belongs to the group of fish commonly known as “Killifish”. The origin of this name is not entirely clear, it probably comes from the Germanic word “kill”, which in the Old Norse form meant a bay or in Dutch a river bed or a water channel. It probably has to do with the fact that these fish live in small, separated bodies of water that dry up periodically. Zagreb eggs can survive a long period of drought and hatch when the rainy season returns.


Africa. Species described from the area near the city of Beira in Mozambique. For many years it was considered widespread in the areas between South Africa’s Kruger National Park and the Kwa-Kwa River north of the Zambezi Delta. Populations from the south and north of this range, showing differences in coloration and morphology, have now been described as N. pienaari ( Black Rachovii ) and N.

krysanovi (orange tail) species. This means that the range of N. rachovii is limited to the area between the Lower Pungwe and Zambezi basins in eastern Mozambique. It lives in ephemeral, water-filled depressions, backwaters and swamps located mainly in lowland flood plains , where the pH of the water is usually 6.0-7.0 degrees. Each year, during the dry season, these habitats dry up completely for several months.

They include plants of the species N ymphea, Ottelia, Lagarosiphon and Utricularia , as well as related fish species N. kadleci and N. orthonotus , as well as Clarias gariepinus (African catfish), Ctenopoma multispine (Climbing perch), Protopterus annectens (Brown lambs) and unidentified barbels (genus Barbus). Some habitats are used by local people to grow rice for their own needs.

Characteristics and disposition

Rakhiv’s scraps reach up to 5.5 cm in total length.

The body is medium-sized, massive, tall and laterally flattened. Dorsal profile slightly concave on the head, convex from the nape to the end of the dorsal fin (more in older males than in younger males). The top and bottom profile of the base of the tail almost straight. At the top of the head is the frontal central supraorbital neuromast system that forms two distinct shallow grooves. Snout pointed, slightly pointing up.

In the dorsal fin 15-17 rays, in the anal fin 15-18. The base of the first radius of the dorsal fin lies with the base of the second or third radius of the anal fin. Abdominal fins short, not reaching the beginning of the anal fin. The pectoral fins reach the beginning of the pelvic fins. On the lateral line, 26-28 scales, 2-3 at the base of the caudal fin, most concave in the middle.

Males have a laterally flattened, high torso. All their odd fins are rounded. Dorsal and anal fins covered with epidermal tissue. On all the rays of the dorsal and anal fins there are glands protruding from the epidermis. The ends of the rays of the dorsal and anal fins do not protrude from the epithelium.

Gill membrane slightly wrinkled protruding from the gill covers. They are more colored than the females. Body color iridescent, variable – depending on the population, from light blue to light blue-green or blue-gray. Orange head and throat to light blue body color. The posterior edge of the scales is orange-red to brownish-red, giving a highly mesh-like appearance.

Dorsal and anal fins pale blue to light blue-gray, further with orange-red to red-brown spots and stripes. Dorsal fin with a narrow blue-white margin. Tail fin pale blue to blue-gray with orange-red to red-brown spots and stripes in the lower half. The black edge of the caudal fin is followed by a brown stripe that changes to a wide orange stripe. Belly fins light blue with a few small red spots.

Pectoral fins pale transparent orange with a light blue margin. The iris of the gold eye with a dark vertical line. Females are smaller than males and have a lower torso. Dorsal and caudal fins are rounded. Rectal fin, triangular, rounded at the tips, set more back than in males.

Absence of epidermal tissue covering the dorsal and anal fins and glands in the rays. The gill membrane does not protrude from the gill covers. They are less colorful than males. Body color olive gray-brown, front scales on the sides with iridescent light blue to silvery centers. All fins are colorless.

The iris of the eye is brown to golden with a dark vertical stripe Fish of the Nothobranchius species grow most of their lives. In the wild, due to the specific conditions in their natural habitats, they only live for a few months. In aquarium conditions, this period can be slightly extended by lowering the water temperature to approx. 20 ° C. On the basis of the conducted research, the median life of Zagrebek Rachov in captivity was 9-12 months.

This time is encoded in genes. The last stage of life begins suddenly, fish are less active, their bodies bend, males lose their bright coloration, and females, which until recently were full of eggs, have sunken bellies.

Nutrition and feeding

Micro predators. In their natural environment, they eat large amounts of larvae and insects. In the aquarium, the basis of the diet should be live or frozen foods, e.g.

daphnia, artemia, waterfowl, grindals (pot-pots), mosquito larvae, etc. Live food is especially important for these fish due to their high energy demand in the period of rapid growth, as well as huge reproductive effort throughout adulthood. They can be supplemented with good-quality dry food in flakes or granules. Rachovii have a large appetite and a fast metabolism, but they shouldn’t be fed too much .


For a couple or a harem, an aquarium with a length of min.

45 cm, for a larger group of min. 60 cm. Dark substrate recommended, but not necessarily peat, which is required for reproduction. Fish should be provided with numerous hiding places. The tank can be partially planted with dense vegetation, and you can add wood, roots or stones.

When arranging decorations, avoid objects with sharp edges that could damage the fins of the fish. Lighting should not be too bright. A cover is also recommended as they can pop out of the aquarium. Zagrebs feel best in soft and acidic water (5.8-7.6 pH, hardness below 10 dGH), but they can also tolerate neutral and slightly alkaline water, and even slightly saline water. Filtering the water through the peat can help to lower the pH.

The optimal water temperature should be in the range of 20-25 ° C. Temperature affects their lifespan. They will live longer in cooler water, and shorter in warmer ones. Like all aquarium fish, they require proper filtration and partial, regular water changes. They should not be released into biologically unstable tanks.

In the aquarium, it is recommended to keep a male with several females. Males are not particularly territorial, but dominant individuals in the wild are likely to define some spawning grounds, perhaps based on the nature of the substrate that ensures the survival of the eggs. The hierarchy is set according to size. Dominant males control the largest areas they actively explore for females. In the aquarium, they often duel with each other, usually they do not hurt each other – they flap their fins, widen the gills or catch each other with their mouths and the weaker male drifts away.

Clashes even take place in large tanks. To spread aggression, in a large group it is recommended to keep more than three males with a predominance of females and to break the line of sight in the tank, e.g. with tall vegetation.


Reproduction of the species of the genus Nothobranchius requires mapping the conditions in their natural environment, also taking into account its seasonality. The Nothobranchius species have developed an interesting reproductive strategy.

The reproductive instinct of these fish is very strong, they start breeding as soon as they reach sexual maturity. To ensure the survival of the population, spawning usually occurs daily for the remainder of adult life. It is very important for these fish to stay active on a daily basis, due to the difficult and changing habitat conditions and the associated high mortality risk. Spawning is initiated by the female, depending on whether she carries mature eggs or not. Natural biotopes are usually cloudy because there are fine particles floating in the water and submerged objects can only be seen from a few centimeters away.

Females have a brownish-gray or brown color, which makes them difficult to see in such conditions. On the other hand, the bright colors of the males make it easier for females to find them. The first contact is followed by a brief presentation and spawning takes place in the next few seconds. The fish swim towards each other, the male especially quickly and vigorously. He also has a characteristic flirty approach.

He tries to push the female towards the ground, impressing at the same time with her extended, elongated fins. He positions himself above the female and presses his lower jaw against the dorsal surface of her head. Encouraged and ready for spawning, the female moves along with it to the ground (otherwise it runs away and flows towards the surface). The male then wraps his fins around the female, pushing her to the ground. The male’s body takes an S-shape, while the female arranges her anal fin in a conical shape and presses it into the ground.

After a few seconds of shaking, the steam remains motionless for a second, and the female, with a quick jerk, releases a single egg, which is fertilized by the male at the same time. This egg-laying sequence may repeat several times. After a few seconds of shaking, the steam remains motionless for a second, and the female, with a quick jerk, releases a single egg, which is fertilized by the male at the same time. This egg-laying sequence may repeat several times. After a few seconds of shaking, the steam remains motionless for a second, and the female, with a quick jerk, releases a single egg, which is fertilized by the male at the same time.

This egg-laying sequence may repeat several times. Adult fish reproduction Breeding adult Nothobranchius fish in an aquarium is possible, but requires some caution and patience. They can be bred in pairs, harems or groups. They can be bred continuously when both sexes are kept together or periodically when split. If males and females have been raised together, they can usually be bred together.

It is best to breed fish in a completely empty aquarium with a bare bottom and some spawning ground in a small plastic container with a diameter of approx. 10 cm. The best substrate is sphagnum moss, which should be scalded and rinsed beforehand. Pour a container with a 2 cm layer of substrate all the way to the top and wait for the tiniest particles to fall to the bottom. It is worth placing a few stones in the container that will weight it down and allow it to sink and keep it at the bottom.

When the peat settles, the container can be put into a previously prepared tank. The use of a container has several advantages. The rest of the aquarium remains completely free, where the fish can be fed freely and excess debris is easily removed. The substrate is easy to pick up and, given the limited container size, contamination is kept to a minimum. In addition, it reduces the amount of peat used, which is another important aspect, especially if you have a large aquarium.

Moreover, in a relatively small amount of peat, we will obtain a high density of eggs. When the fish reach sexual maturity and the appropriate size, place a container with sphagnum in the tank. Spawners usually find entry into the container quickly. The reproductive instinct of the species is very strong and we can always expect to spawn under optimal conditions. Females carrying mature eggs will swim into the spawning box and gently nibble the peat fibers for a suitable spawning site.

Males chase after females as well as compete with each other. If too much aggression occurs, fish can be separated by sex over several days. Fish reared together show greater tolerance. In a larger group, a dominance hierarchy forms among the males. If there are only two males in the group, the weaker individual will be exposed to constant attacks of the dominant.

In the case of a group of several males, the aggression will spread to several individuals, and weaker males will have a better chance of escaping. Breeders’ experience has shown that injured specimens are seen less frequently in large groups. Wild individuals are generally more aggressive towards each other. Another approach to breeding could be to split up by sex early and pool for short spawning periods in a separate tank. The easiest way will be to catch, in a separate aquarium, young males, which are the first to show signs of coloration.

Keep in mind that the time of fry development may vary, so it should be done gradually over a period of several weeks. Faster developing individuals will stain first, others may only show colors after removing the dominant males. The gender distinction is unlikely to be a major problem. Gender can be recognized even at a very early stage, before the fish begin to stain, as females have a very characteristic elongated triangular anal fin. In the case of breeding with the combination of fish for short spawning periods in a separate tank, you can use a container with peat or cover the entire bottom with it.

The contamination of the substrate will be limited anyway, as the feeding would take place in the breeding aquarium. Females usually lay eggs within a few hours of being released, after which time the fish can be split up again or replaced with another pair. When the fish are fed a variety of live foods, this can be repeated approximately every other day. Storage of eggs After a week or two, the peat with the container can be removed from the tank and replaced with another batch. After removing the peat, put it in a mesh bag with fine meshes and gently squeeze it out of excess water.

The eggs have a hard and durable shell, so squeezing them gently shouldn’t hurt them. Peat should maintain a certain level of moisture, but at the same time should not be too wet. If necessary, it can be dried on a paper towel for several hours. Once prepared, it can be closed in a plastic bag and stored. The bag should be labeled with the species name, site code and date of collection.

It is best to store it at 23-25 ​​° C. A lower temperature will extend the development time, a higher temperature will speed it up. In contrast, temperature extremes will be detrimental to egg development. Occasionally unfertilized eggs may occur, which turn white and disappear within a week. Therefore, after a week or two, the bag can be reopened to determine the final number of eggs.

Healthy eggs are clean and transparent, usually easily visible in brown peat. The bag can be checked regularly during storage, and when we see developed embryos, the eggs are ready to hatch. The development time of Nothobranchius eggs depends on the species and is adapted to the length of the dry season in nature. Species in long dry season regions will have a long incubation time, sometimes up to ten months, while those in wet regions with multiple rainy seasons will have a shorter development time, sometimes only two months. In addition, several environmental factors such as temperature, peat moisture and the amount of available oxygen affect the incubation time.

In Zagrebka Rachov the period of embryonic development at room temperature is about 5-7 months. In too wet peat, water fills the free spaces between the fibers, it decomposes, which in turn leads to the creation of anaerobic conditions. In such an environment, the eggs cannot develop and the so-called diapause. Especially in fine, compacted peat, the development of eggs can take an unusually long time. Its slight drying will accelerate this process.

In too dry peat there is a risk that the eggs will die off, to prevent this from happening, you can add a little wet peat to the bag and mix it together. Hatching eggs Before the planned hatching date, it is worth checking if there are well-developed eggs in the peat. In the eggs ready to hatch, you will see large black dots with silver fringes – the eyes of the fry. They herald the arrival of a simulated rainy season. Eggs undeveloped will appear transparent.

A few days before hatching, you should set up a separate tank and fill it with moderately hard water up to about 10 cm in height. A small sponge filter is sufficient for filtration. Harder water increases the resistance of the fry to velvet disease ( Oodinium ), which is often seen in soft water aquariums. If soft water is used, a little salt may be added. The fry immediately after hatching begin to eat, it is recommended to feed live, freshly hatched brine shrimp larvae.

For hatching fry, it is best to pour water from a previously prepared tank into a shallow plastic container. Depending on the amount of peat, pour water about 4-5 cm in the container. Then put the peat with roe in a container. Peat supports the hatching process, so there must be enough peat in the container and can be added if necessary. Eggs without peat often do not hatch at all.

Most of the wet peat with roe will sink immediately, the floating debris can be gently broken so that all the eggs sink to the bottom. In nature, the ground is moistened by the first rains, which herald the rainy season. Sometimes it gets soaked before the peak of the rainy season, triggering the final stage of egg development. Therefore, under farming conditions, peat can be sprayed with water before hatching. Hatching occurs within 30 minutes to several hours after soaking.

Right after hatching, the fry are most often hidden in the peat. A successful brood can be confirmed, for example, by gently tapping the container, causing a stir among the fry. A few hours after hatching, the fry begin their first swimming attempts, which at the beginning end with a quick sinking to the bottom, until the swim bubble is filled. It does not need atmospheric air for this purpose, so direct access to the water surface is not necessary. Peat is best soaked in the late evening, before turning off the lights.

In the morning there should already be a lot of fry floating. In nature, it is not always more rainy after the first rain. If the habitat dried out too quickly, the newly hatched fry might not survive. Therefore, the development time of the embryos varies, some of them remain at an early stage awaiting the next rains. Thus, in nature, the species Nothobranchius can survive even the most unfavorable conditions.

After soaking, peat moss should be dried again and stored for a few more weeks, as it may contain undeveloped eggs that are in a state of rest. Subsequent soaks often increase the amount of fry obtained. This is especially typical of species originally living in arid regions. The eggs of species from wet regions or with multiple rainy seasons tend to have a reliable development time and most of the fry hatch the first time they are soaked. Raising fry The fry immediately accept the newly hatched Artemia larvae.

It should be fed in small portions so that they are eaten in the shortest possible time. The fry’s filled pink belly indicates that the food is being eaten properly. Although brine shrimp larvae can survive for a short time in slightly salted water, overfeeding can lead to its contamination. This, in turn, contributes to the occurrence of velvet disease, which is particularly dangerous for the life of tiny fry. From the observations of breeders, it is usually responsible for massive losses.

Snails can be helpful in keeping order and they will eat leftover food. Feeding in small portions several times a day is recommended. Approximately one day after hatching, the fry are moved to a previously prepared aquarium with a low water level, it will make it easier for the fry to find food. After about a week, you can gradually increase the water level. A small daily change is also recommended.

When doing this, you can remove the remains of food with a thin tube, sucking them from the bottom. After two weeks, when the fry are growing well, we gradually increase the amount of water changed. As we grow, we give larger and larger food, e.g. pot plants, black, white and red mosquito larvae. It is very important to provide a varied diet rich in nutrients.

A balanced diet will ensure that even the smallest females will develop properly so that they can lay eggs later. The development of the fry is extremely fast. In captivity, males begin to color after approx. 3-4 weeks, depending on the temperature, the space provided, as well as the quality and quantity of food. At the age of 6-8 weeks, they can be sexually mature.

In nature, where conditions are optimal, development is even faster. In the aquarium, however, they can survive a little longer and, thanks to their constant growth, grow to larger sizes. When males reach sexual maturity, they can be separated from the rest of the group to increase the chance of survival and proper development for smaller females. If we have a lot of space, there are no obstacles to keep together. It is worth paying attention to maintaining a good breeding line, so you should remove specimens with deformations, e.g.

with an inappropriate body structure or strange coloration. While growth in aquariums appears to be rapid, it is actually slower than growth in the wild. In an aquarium, fish have much less space than in nature. For this reason, there may be minor injuries that almost never occur in nature. In the wild, the sex ratio of the fry is mostly balanced, while in the aquarium it can deviate one way or the other.

This is most likely due to extreme conditions during the incubation of the eggs or during the rearing stage. In captivity, a slight male advantage can usually be expected. Perhaps it is because females are smaller and weaker, and therefore more sensitive than males, or because they grow slower and can be eaten by them.


Nothobranchius species are very susceptible to velvet disease, which is very difficult and often impossible to cure. This disease often appears in neglected aquariums with soft, acidic, rarely changed water.

It can be prevented by keeping the fish in medium-hard, slightly alkaline water (above pH 7) or by adding non-iodized salt to the water – no more than one teaspoon for every 5 liters.


Nothobranchius Rachovii varieties are marked with some form of code in order to distinguish them and thus reduce the possibility of hybridization. For example, the ‘Beira 1998’ comes from a commercial harvest in 1998 in the Beira (city) area of ​​eastern Mozambique. In the case of the varieties described as MOZ 99/1, MOZ 99/2, MOZ 99/3 etc., “MOZ” means “Mozambique”, “99” year of harvest (1999) and the last digit is the place of harvest. Fish of unknown origin or hybrids are generally referred to as an aquarium strain.

The putative subgenus Zononothobranchius , to which N. rachovii was previously attributed , now contains only one species known as Nothobranchius rubroreticulatus , according to mtDNA analyzes by Shidlovskiy et al. (2010).


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