Redtail notho

Aquarium fish: Redtail notho (Nothobranchius guentheri)
Size: 3.5 cm
Origin: Africa
Water temperature: 20-27 ° C
Aquarium volume: 40 l

Redtail notho (Nothobranchius guentheri ) – a small, beautifully colored, short-lived aquarium fish from the  Nothobranchiidae family . Belongs to the group of fish commonly known as “Killifish”. This nomenclature probably comes from the Germanic word “kill”, which in the Old Norse form meant a bay, and in Dutch a river bed or a water canal. It is probably related to the existence of these fish in small, limited water reservoirs, which periodically dry up. Zagreb eggs are extremely hardy and can survive long periods of drought, and they hatch when the rainy season returns.


Africa. Endemic species, it occurs only in periodic backwaters, swamps, ditches and small streams on the island of Unguja in the Zanzibar archipelago in eastern Tanzania. Every year, during the dry season, the places of occurrence dry up almost completely for several months. The water in places of occurrence is usually cloudy, has a temperature of 25-29 ° C, pH 7.2-7.7 and conductivity 140-980 µS.

Characteristics and disposition

African Zagrebs are up to 4.1 cm in total length .The body is moderately tall, compressed – the highest one just behind the base of the pectoral fin.

Dorsal and ventral profiles slightly convex from the snout to the rear end of the epiphyses of the dorsal and anal fins, almost straight at the base of the tail. Jaws short, with numerous irregularly arranged teeth. Mouth slightly pointed when viewed in the upper position. In males, the dorsal and anal fins are wide, rectangular, rounded, with short threadlike rays. In females, the dorsal fin is rounded, the anal fin is triangular and slightly longer than the dorsal fin, and the pectoral fin is elliptical.

Belly fin is small. In males, rows of well-developed sensory nipples along two-thirds of most of the rays of the anal fin. The beginning of the dorsal fin at or slightly in front of the anal fin. In the dorsal fin 15-16 rays, in the anal fin 15-16. Body and head completely covered with small cycloid scales, except for the ventral surface of the head.

On the medial lateral and latero-central parts of the head in males, thread-like contact organs are located along the posterior edge of the scales. No scales at the base of the dorsal and anal fins. Front scales arranged irregularly. 27-28 scales in the lateral line; 14 rows of scales around the caudal peduncle; a single longitudinal row of scales between the anterior supraorbital row of neuromasts. 27-28 scales in the lateral line; 14 rows of scales around the caudal peduncle; a single longitudinal row of scales between the anterior supraorbital row of neuromasts.

27-28 scales in the lateral line; 14 rows of scales around the caudal peduncle; a single longitudinal row of scales between the anterior supraorbital row of neuromasts. Males have a bluish-green iridescent body, light greenish to the side, blue to light blue, almost white in the front. Posterior edge of scales red, forming a red mesh pattern, often indistinct at the front and progressively more pigmented at the rear. The red stripes overlap the red mesh pattern between the pelvic fins and the posterior part of the caudal fin peduncle; the front stripes are slightly curved, the back stripes are almost straight. Light brown back, white belly, light greenish-blue side of the head.

Dorsal and ventral parts of the head pale yellow red pigmentation forming a reticulated pattern in the retroorbital area with three distinct oblique short red stripes; light blue iris of the eye. Dorsal fin light blue, with red dots and short irregular stripes, with a black border and a white border. Rectal fin pale greenish or orange-yellow, basal part bluish-white, with red dots, spiral marks and short, irregularly arranged stripes, edges pale yellow. The caudal fin is intensely red, with a black posterior edge. Pectoral fin is transparent yellow, with a blue-white edge.

Belly fin pale yellow or red with a yellow edge. Females are more modestly colored, the body is pale brown without markings. The posterior border of the scales is pale greenish, the back is pale brown, the belly is white, the head is pale brown, the eye area is pale greenish, bluish. Blue and white iris, transparent fins. Fish of the species Nothobranchiusthey 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 average life expectancy of African Zagrebs in captivity was 43 weeks, and the maximum life expectancy was 64 weeks. This time is encoded in genes.

Interestingly, scientists managed to extend this life expectancy to an average of 51 weeks and a maximum of 82 weeks. They administered to the test subjects with food resveratrol – a natural chemical compound of plant origin. The last stage of life of these fish begins suddenly, they are less active, their body bends, males lose their bright coloration, and in females, until recently full of eggs, their bellies disappear.

Nutrition and feeding

Micro predators. In their natural environment, they eat a large number of larvae and insects.

In an aquarium, their diet should be based on live or frozen foods, e.g. daphnia, artemia, waterfowl, grindals (pot-pots), mosquito larvae, etc. reproductive effort throughout adulthood. They can be supplemented with good-quality dry food in flakes or granules. Zagrebs have a great appetite and a fast metabolism, but they shouldn’t be fed too much .


For a couple or a harem, an aquarium of min. 45 cm long, for a larger group of min. 60 cm, with a dark substrate, not necessarily peat, which is nevertheless required for reproduction. Fish should be provided with numerous hiding places. The tank can be partially planted with dense vegetation, decorated with wood, roots or stones.

Objects with sharp edges that could damage the fins of the fish should be avoided. Lighting should not be too bright. It is also advisable to cover the aquarium with a cover. African Zagrebs feel best in neutral to slightly alkaline water, approx. 7 pH and 5-10 dGH hardness.

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. Interestingly, in the natural environment there can be rapid temperature fluctuations in the range of 16-32 ° C. Water temperature affects their lifespan. They will live longer in cooler water in this range, while in warmer water they will live shorter.

Like all aquarium fish, they require proper filtration and partial, regular water changes and should not be placed in a biologically immature tank. In the aquarium, it is recommended to keep the male accompanied by several females. Males are somewhat territorial, in the wild, dominant individuals probably define some spawning grounds, perhaps based on the type of substrate, which will increase the chances of egg survival. The hierarchy is determined by size. Dominant males control the largest areas they actively search for females.

In the aquarium, they often duel with each other, usually without hurting themselves – they flap their fins, widen the gills or wrestle with their mouths, and the losing male drifts away. Skirmishes even take place in large tanks. To spread aggression, it is recommended to keep more than three female-predominant males in large groups and to break the line of sight in the aquarium, e.g. with tall vegetation.


In order to reproduce the species of the genus Nothobranchius , seasonal conditions in their natural environment should be mapped.

Nothobranchius species have an interesting reproductive strategy. These fish have a very strong reproductive instinct, they start breeding as soon as they reach sexual maturity, and they often spawn every day for the rest of their adult life. Maintaining such intense activity is very important to ensure the survival of the population in difficult natural conditions with a high risk of mortality. Spawning is started by a female that carries mature eggs. Natural biotopes are usually not very transparent, fine particles are floating in the water, and submerged objects can only be seen from a short distance.

In such conditions, males find it difficult to see brownish-gray females, while the bright colors of males are easier to see. After the first contact, there is a brief show and spawning takes place in the next few seconds. The fish get closer to each other, the male especially quickly and vigorously. At the same time, it shows a characteristic flirtatious approach. He pushes the female towards the ground, impressing at the same time with its large fins.

He positions himself above the female and presses his lower jaw against the dorsal part of her head. The eager and ready female moves with him to the ground (otherwise it runs away). The male then wraps his fins around the female, pressing it against the ground. The male’s body takes an S-shape, while the female arranges her anal fin in a conical shape and pushes it into the ground. After a few seconds of trembling, the steam freezes for a second, and the female, with a quick jerk, releases a single egg, which is fertilized by the male at the same time.

During spawning, such an act may occur several times. Adult fish reproduction The breeding of adult Nothobranchius fish requires, above all, 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 they are separated. Males and females raised together can usually also be bred together.

It is best to breed fish in a “naked” aquarium without decorations and with a little substrate in a small plastic container with a diameter of about 10 cm. A 2 cm layer of scalded and thoroughly rinsed sphagnum moss is best as a substrate. Pour water over the container and wait for the particles to fall to the bottom. Adding a few stones to the bottom will prevent it from flowing out. When the peat settles, the container can be put into a previously prepared tank.

The use of a container has several advantages. In the remaining space, the fish can be fed freely, which facilitates the removal of contaminants. With the limited size of the container, the substrate can be easily collected, minimizing its contamination. In a relatively small amount of peat, we obtain a high density of eggs. Place the container with sphagnum in the tank when the fish reach sexual maturity.

Spawners usually find the entrance to the container quickly. Their reproductive instinct is very strong and spawning can always be expected under optimal conditions. The females are the first to enter the container and nibble at peat fibers, preparing the spawning site. Males chase after females and compete with each other. In case of too much aggression, fish can be separated by sex for several days.

Within the group, a dominance hierarchy is formed among the males. If there are only two males in it, the weaker individual will be exposed to constant attacks from the dominant. With many males, aggression will spread and weaker individuals will have a better chance of escaping. In the experience of breeders, wounded specimens are less frequently observed in large groups, Another breeding method may be to separate the fish by sex early and pool them for short periods in a separate spawning tank. For this purpose, it is easiest to catch young males that are the first to show signs of coloration.

It should be remembered that the time of development of the fry varies and the faster developing individuals color first, and the others will show their colors only after removing the dominant males. Therefore, harvesting should be done gradually over a period of several weeks. The gender distinction is unlikely to be a major problem. Even at a very early stage, before the fish begin to color. Females have a very characteristic elongated triangular anal fin.

In this case, you can either use the sphagnum moss container or cover the entire bottom with it. As the feeding takes place in a separate aquarium, the contamination of the substrate will be limited anyway. Females usually lay eggs within hours of being released. After spawning, the fish can be split apart or replaced with another pair. When the fish are well-fed with varied live food, the amalgamation can be repeated even every other day.

Storage of eggs After a week or two, the peat container can be removed from the aquarium and replaced with a new batch. Place the removed substrate in a mesh bag (with fine meshes) and carefully drain off excess water. The eggs have a hard, durable shell, so squeezing them gently should not damage them. The peat should be moist, but at the same time it should not be too wet. If necessary, it can be dried on a paper towel for several hours.

Prepared in this way, it can be closed in a string 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.

Unfertilized eggs turn white and disappear within a week. After a week or two, the bag can be reopened to determine the final number of eggs. Healthy eggs are clean and translucent, usually easily visible in a brown base. The bag can be inspected 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 from 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 N. guentheri , the embryonic development period at 24 ° C is about 10-12 weeks. 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 those ready to hatch, you will see large black dots with silver rims – the eyes of the fry. Eggs undeveloped will appear transparent. A few days before hatching, you should set up a separate tank and fill it up to the level of approx. 10 cm with moderately hard water. Harder water increases the resistance of the fry to velvet disease ( Oodinium ), which is often seen in soft water aquariums.

Alternatively, a small amount of salt can be added to the soft water aquarium. It is enough to use a small sponge filter for filtration. For hatching, 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. Then put the peat with roe in a container.

The substrate supports the hatching process, and eggs without peat often do not hatch. Therefore, there must be enough of it in the container and can be refilled if necessary. Most of the wet peat sinks immediately, the remaining floating particles can be gently broken so that all the eggs sink to the bottom. In nature, the soil is often wetted with the first rainfall of the rainy season before it reaches its peak, triggering the final phase of egg development. In order to reproduce these conditions, peat can be sprayed with water before the planned hatching.

After soaking, the eggs hatch within 30 minutes. up to several hours. At first, the hatched fry are most often hidden in the peat. A gentle tapping on the container will make it move, which will confirm a successful brood. After a few hours, the fry make the first swimming attempts, which end up quickly 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. It is best to soak the substrate late in the evening, before turning off the light. In the morning there should already be a lot of fry floating. In nature, it is not always heavy rainfall after the first rain. When the soil dries too quickly, freshly hatched fry may not survive.

Therefore, the time of embryo development varies, some remains in an early stage awaiting the next rains. In this way, the Nothobranchius species can survive even the most unfavorable conditions. After soaking, sphagnum 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 attempts often increase the number of fry obtained. This is especially true of species naturally occurring in arid regions.

The eggs of species from humid regions with many rainy seasons tend to have a reliable development time and most of the fry hatch at the first opportunity. 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, they 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.


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