WildNothos
THE NOTHOBRANCHIUS SITE
INTRO - DISCOVERY & EARLY HISTORY - DISTRIBUTION & BIOGEOGRAPHY - ECOLOGY & BIOTOPE - LIFE HISTORY & REPRODUCTION - MAINTENANCE & BREEDING - TAXONOMY & SYSTEMATICS
When keeping and breeding the species of the genus Nothobranchius, we need to simulate the conditions of the seasonal natural biotopes and take into account their annual life history traits.
Maintenance and Breeding of Nothobranchius Fishes
In order to prepare the most suitable conditions for maintenance and breeding of Nothobranchius fishes in captive environment, we need to consider the seasonal mode of reproduction that these fishes have developed, and which is completely adapted to the alternation of the rainy and the dry seasons of the natural habitat. In order to ensure the maintenance of a species over several generations, the naturally occurring dry season and rainy season need to be simulated in our fish room. This means that a suitable spawning substrate should be provided for the fish, which medium then needs to be dried to provide the proper conditions that ensure the development of the eggs during a simulated dry season. In captive conditions, several types of spawning mediums exist, and peat moss is probably the most often used substrate, and this is also my personal preference.
The typical substrate in Nothobranchius habitats in the nature comprises fine dark mud, with suspended clay particles, rather than peat moss. However, the use of peat as spawning medium in captivity has the advantage that it is relatively clean and represents a convenient alternative to mud, which latter tends to be messy to work with, rendering the water turbid.
During the spawning activity, the fish will deposit the eggs into the peat moss. The spawning substrate, containing the eggs, is then removed from the tank. It needs to be dried to the desired moisture level and stored at proper temperature until the end of the development period of the eggs. The development time is variable, depending on the particular species involved and storing conditions, but it usually takes several months.
Transporting a bag of peat, containing eggs, is an easy way to propagate Nothobranchius species, and for many hobbyists this is the most commonly practiced way to acquire a desired species. Therefore, I start the account of the maintenance and breeding from that step of having received a bag of peat with eggs. The following text is the description of my method, which works well for me but some adaptations might be needed according to local conditions of everyone. The description of the life cycle begins with the simulation of the starting rainy season, that is wetting the peat containing the eggs, which process can be carried out in the following manner.
Hatching the Eggs
Before hatching, the best is to examine if there are well-developed eggs in the peat. The incubation time varies depending on the particular species involved because they are adapted to the general climatic conditions and the length of the dry seasons in the nature. The duration of the dry period in the different tropical and subtropical regions of Africa varies between around two to six months and, in some exceptional cases for particularly dry areas, it can be even longer. Therefore, the egg development will largely follow the pre-programmed potential period of aridity. Indications for embryonic development per species are mentioned in the species accounts. As the development of the eggs would invariably take several months, breeding Nothobranchius fishes require a certain degree of patience.
In addition to the variation by species, the development time of the eggs also depends on the storing conditions. For instance, the temperature during the development phase can significantly influence the incubation period. I keep the peat bags with the eggs at room temperature of about 22-23 °C. There is some tolerance for a few degrees but much lower temperatures will considerably slow down or stop the egg development, whereas much higher temperatures would lead to accelerated development but, in some cases, could also result in fry with malfunctions, such as swim bladder problems.
When the eggs are ready to hatch, the eyes of the fry are visible in the eggs. Eggs that are not developed yet will appear clear. Therefore, if you see the big eyes with the silver rings around them in the eggs, you can be certain that the small fry are ready for the arrival of the simulated rainy season.
A few days before the planned hatching, I set up an aquarium and fill it to a level of about 10 cm with moderately hard tap water and implement a simple sponge filter. I prefer moderately hard water to soft water as it would increase the resistance of the fry against Oodinium, a disease also commonly called as velvet, and which can be often observed when using too soft water, and to which disease the Nothobranchius species are particularly prone. In case of using relatively soft water, a small amount of salt should be added. The hatching itself can be then carried out with some water taken from this previously prepared setup tank, when the filter has already been running for a few days.
Since the small Nothobranchius fry can take food shortly after hatching, we also need to be well prepared to provide them adequate live foodstuff. With the exception of the species of the subgenus Aphyobranchius, generally all Nothobranchius species are capable to consume freshly hatched brine shrimp nauplii soon after hatching. Therefore, it is an important condition to have the live food ready by the estimated time when the fry would hatch. For the species of the subgenus Aphyobranchius, it may be as long as two weeks after hatching before the fry are large enough to take the smallest brine shrimp, so a well-established culture of infusoria and green water should be prepared.
For hatching, I take mature water from the previously prepared tank into a shallow plastic container. Depending on the amount of the peat, I fill the hatching container for about 4-5 cm with water. Then I place the peat with the eggs into the hatching container. I make sure that there is sufficient amount of peat when wetting the eggs because the presence of peat helps the hatching process and eggs without peat will often not hatch at all. I might add extra peat if necessary. Most of the wet peat with the eggs would sink immediately and I gently break up the lumps to ensure that all eggs are free, and they can sink. The rest would sink in a day or two anyway but sometimes I take off the floating elements. In nature, the first rains of the rainy season would wet the substrate but might be soaked before the peak of the rainy season arrives. This might induce the last development phase of the eggs, indicating the arrival of the rainy season. Under captive conditions, I sometimes spray some water on the peat, about a week before hatching. A wetter peat would then sink also more rapidly when placed in the water of the hatching container.
If the time was right, fry usually hatch between 30 minutes and a few hours after wetting. Shortly after hatching, the fry would tend to hide in the peat. If we tap gently the hatching container, the hatched-out fry would move around, confirming positive hatching results. It could take some hours before the fry are able to swim normally. The fry would try to swim right after hatching but first tend to sink back repeatedly until finally manage to fill the swim bladder. To do so, Nothobranchius fry do not need atmospheric air, so direct access to the water surface is not necessarily needed. I always wet the peat late in the evening before switching off the light and going to sleep. This way, I have lot of small fry swimming around early morning.
In nature, the first rain is not always followed by a more abundant rainfall and the newly hatched little fry could die if the habitat would dry out too quickly again. Therefore, the embryos do not develop at the same pace and some of them remain resting in an early developmental stage awaiting the next rains. This way, the survival of the Nothobranchius species in the nature can be ensured even when especially unfavourable, exceptional or erratic conditions would occur. In order to simulate again the natural processes, the peat moss should be re-dried again after wetting. It can be stored away for a few additional weeks because it can still contain viable, undeveloped eggs that are still resting. Multiple wettings often yield additional fry. This is especially typical for species with longer incubation time that originally live in the drier regions. Eggs of species that are from regions with wetter conditions or from areas with two rainy seasons per year tend to have more reliable development time and most of the fry would hatch together at the first wetting.
Raising the Fry
The fry can be fed immediately with freshly hatched brine shrimps. Since the hatching time of brine shrimps can usually take up to 12-48 hours, depending on the temperature, ensure setting up the hatchery on time. Only so much food should be provided at a time, which the small fry can consume within a short period of time. The small shrimps might remain live for some time in slightly salted water but overfeeding will result in dead food that starts decomposing quickly and polluting the water. Polluted water helps the appearance of the velvet, which disease has disastrous consequences for the survival of the tiny fry. If mass death of fry occurs, it is usually accounted for that disease. An exception to first food requirement represent the fry of the species belonging to the subgenus Aphyobranchius. They would be able to consume newly hatched brine shrimp only from an age of about two weeks, so they should be fed with microscopic live food for the first two weeks.
If the small fry are eating well, they will develop a nicely filled pink belly, indicating that they consumed baby brine shrimps. I usually feed the fry two or three times a day in the hatching container for at least one day. On the second day, I gently transfer the fry with a spoon into the previously prepared tank, where the fry will be raised. I do that by placing a spoon near the fry at the water surface and push down one side of the spoon, by creating a small vacuum and so the water, with the fry, rushes into the spoon. For this operation I also use a light shining horizontally into the water of the plastic hatching tray. The side lighting makes the fry much easier to see.
In the raising tank I keep the water level relatively low for the first week, it covers the sponge filter but not much higher than that. The fry are tiny and they find easier the food when the depth of water is relatively small. I introduce about a dozen of small snails to clean up any uneaten food from the bottom of the tank. It is recommended to feed smaller portions but several times a day.
After about a week, the water level can be increased gradually. I do it in a way that I siphon off any visible residue from the bottom of the tank by using a thin plastic tube, removing only with a small amount of water. Then I fill back a little bit more water at a time, than the previously removed quantity. The replacement water is taken from a container where the water has been aged for some time. For about a week, I only carry out small water changes. When the fry reach the age of about two weeks, and they grow well, they fill their bellies with brine shrimp at each feeding, their condition is more stabilized and the volume of the water change can be gradually raised.
As the little fish grow, I continue to supplement their initial diet of brine shrimp nauplii with larger food items, first with grindal worms, then with black, white and red mosquito larvae and planktonic crustaceans collected from outdoor ponds. It is very important to provide a varied and abundant diet of nutrient-rich live food. It would also ensure that even the smaller females could grow out properly, being capable to develop eggs later on. The development of the Nothobranchius species is extremely fast. Under captive conditions, males start to colour up after about three to four weeks, depending on temperature, provided space, as well as quality and quantity of food. At an age of about six to eight weeks, they might be sexually mature. In the nature, the conditions for the growing fry are more optimal and the development of the fish is faster. In the aquarium, however, they might live somewhat longer and, by growing continuously, they can reach considerable size. When the males start to sex out, they might be separated from the rest of the group, in order to give an opportunity to the smaller females to grow out and develop properly. However, if the space provided to the group is large enough, they can be raised together, which I do very often. We need to pay attention to maintain a good breeding line, so I usually cull out specimens with deformations or with inadequate body shape or strange colouration. That way we certainly end up with an optimal breeding group. I always try to maintain a breeding line that resembles the most the colour pattern of the original wild population.
While the development of the Nothobranchius fishes in the aquaria is invariably fast, it is in fact slower when compared to the growth in natural conditions. When a couple of fish is placed in a separate tank, we might think that there is sufficient space available to them. However, when compared to the potentially available space in the nature, in most cases this is not the case. Under captive conditions, minor injuries and torn fins can also happen. In the wild, these kinds of injuries are almost never observed.
In optimal case, the sex ratio between males and females will remain mostly equilibrated. However, in aquaria the proportion of the sexes might be biased in one or the other direction, which could be due to the possible extreme conditions either during the incubation period of the eggs or when raising the fish. I try to avoid providing extreme conditions and, typically, I experience rather equilibrated sex ratio. When raising a group, however, a slight majority of males can be expected. This might be because the smaller and weaker females could be fallible, or the larger mates, usually males, can even consume the smallest specimens, which would be typically smaller females.
An exception to above raising method represents Nothobranchius ocellatus, which is a large predatory species. The fry are large compared to the other species of the genus. The fry will eat each other when kept together, so they need to be isolated in separate containers or tanks within a day after hatching. Each of them needs to be then raised individually.
Special treatment is needed also for the species belonging to the subgenus Aphyobranchius. Likewise, the surface-dwelling behaviour of their parents, the fry tends to rise to the water surface upon hatching and will stay there. Additionally, the fry is very tiny and require microscopic food for the first period after hatching, usually about two weeks. Therefore, we need to provide them very small food and we need to get the food near the surface level. The small food can be Paramecium or green water. To get the food to the fry, the air bubble of the sponge filter will make the job, when the bubble is set to a rate when it gently mixes the water and carry the microscopic food to the fish in the upper water level. It will take up to two weeks that the fry will move away from the water surface and will have a size when they will be able to consume newly hatched brine shrimps. Depending on the difference of the growth rate within the group, it might take a few days, until gradually all the fry can switch to brine shrimp. The rest of the development will be quick, and sexes can be identified a few weeks later.
Maintaining the Fish
I keep groups of young adults and smaller breeding groups usually in 40 l tanks. Smaller tanks can be used to house few fry, a couple or a trio of adults. For practical reasons, I keep the bottom of the aquarium bare. This makes me easier to keep the tank clean, by syphoning off any visible dirt from the bottom of the tank. It also avoids the undesirable effect of the fish spawning to the bottom substrate everywhere in the tank. For lighting, I do not illuminate directly any of the tanks; there is only a ceiling light in the room. With the absence of substrate and light, I do not keep plants in the tanks. For filtration, I place in the tanks simple air driven sponge filters.
The temperature of the fish room is around 22-24 °C on average throughout the year, and I do not use additional heaters in the tanks. The temperature can be somewhat warmer during hot summer period. Within the range of room temperature, the tanks in the higher ranks are slightly warmer whereas at the bottom rank somewhat cooler. I found that some species like higher temperatures, including some of the Nothobranchius species originating from relatively hot regions, such as N. virgatus from Sudan, or some species from the coastal part of Tanzania, such as N. eggersi, which species I typically try to allocate in the tanks at the highest ranks, close to the ceiling. These fishes will thrive in warmer environment and I observed that egg production will be significantly lower when temperature drops. For some other species that usually inhabit shaded and vegetated edge of slowly flowing small streams in the nature, such as N. robustus from Uganda or N. symoensi and N. rosenstocki from Zambia, I have good success when I keep them in the tanks at the bottom, which experience somewhat cooler temperature. The main factor for the success is probably not so much the temperature but the associated dissolved oxygen content; the cooler the water, the more dissolved oxygen it can hold. Despite the somewhat cooler temperature, the latter mentioned species thrive in that environment and produce considerable number of eggs every week. The somewhat cooler temperature has also the advantage that these fishes live also relatively longer.
In all my tanks for Nothobranchius fishes, I use my standard tap water, which is moderately hard and slightly alkaline. Before water changes, I age the tap water in a large plastic container for about a week. Most Nothos will do well in that hard and alkaline water, although I don't think that the pH is a critical issue, provided it does not become too acidic. Therefore, I do not necessarily try to duplicate exactly water conditions found in natural Notho habitats in the wild. Our tanks are systems in much more restricted volumes than natural habitats and we should try to establish an ecosystem with sustainable conditions in the restricted system.
I try to feed my fish exclusively with live food, which contains daily portions of artemia nauplii and grindal worms. I often supplement the diet with food that I collect from nearby outdoor pools, such as planktonic crustaceans and different mosquito larvae. I keep a large plastic container in my garden, where I regularly enter a portion of the small invertebrates collected from the pond. From that container in the garden I then take every other day or so a smaller amounts of microinvertebrates, in order to provide a more varied diet for the fish. I always have a small stock of frozen red mosquito larvae in the freezer, which I only feed in exceptional cases, when I have no access to sufficient amount and variety of live food, but this is relatively rare.
Breeding the Adults
Breeding adult Nothobranchius fish within the confines of an aquarium is a task requiring some prudence but it can be accomplished without any major difficulties. Fish can be bred in pairs, in trios or in breeding groups. They can be bred on a permanent basis, keeping the sexes always together in the same tank, or they can be spawned on a temporary basis when the sexes are kept separately and brought together frequently for short period of time. If the males and females of a species have been raised in a group they can usually be kept together for breeding.
My method of breeding is to use a completely empty tank with bare bottom and with some spawning substrate that is placed in a plastic container. For spawning medium in the tanks I use exclusively peat moss. The peat is first wetted in boiling water, and then thoroughly rinsed before being placed in the aquarium. Spawning container can be a plastic ice-cream container or similar plastic box of about 10 cm in diameter. The peat is rinsed and then placed in the container for about 2 cm thickness. After the peat was introduced into the container, I fill up with water right to the top and leave if for a few minutes, so that the small peat particles can settle down. I also place in the container a couple of small stones, which would help to sink the container and keep it on the bottom of the tank. Once the peat is settled down, I lower the container slowly into the tank. The use of a plastic spawning container has, in my opinion, several advantages. The rest of the tank can be kept completely free, where the fish can be fed and excess dirt easily removed. The peat can easily be collected by removing the container and in the limited volume of the plastic box the contamination of the spawning substrate would stay reduced to a minimum. Furthermore, the amount of peat can be optimized which is another important aspect, especially if the aquarium is large. In addition, the eggs get concentrated in the relatively smaller amount of peat.
Once the fish reach sexual maturity and adequate size, I place the spawning container with the peat in the tank. The fish would usually find their way quickly to enter the small container. The reproductive instinct of the Nothobranchius species is strong and, under optimal conditions, we can always expect that spawning would take place in a breeding setup. The fish will soon begin with the initial spawning activities. Females carrying mature eggs would enter the spawning container and gently pecking on the peat fibres when looking for suitable spawning site. Males drive the females strongly, while males would also compete against each other. Minor injuries might happen, and sexes might be separated for a few days, if necessary. If we keep a group of males and females together, the males usually develop a hierarchy of dominance. When specimens are raised as a group, they seem to tolerate each other better.
However, if there are only two males in a group, the weaker male is exposed to constant attack by the dominant male. In case of a group with several males, there will be a continuous battle of several participants but the fighting would spread among the individuals and weaker males might have a better chance to escape. According to my experience, beaten or injured specimens can be less often observed in larger groups. In case of having only a couple of females, I often keep them with several males. By doing so, the males keep each other busy, rather than only driving the females.
Wild-caught specimens are generally more aggressive to each other while males raised together in the same tank can more peacefully tolerate each other.
Another breeding method, which I use in some occasion, is to separate the males and females already in the raising tanks and bring them together for short periods of spawning in a separate tank. The easiest way to separate sexes is to cull out from the raising tank the young males, which start to show the first signs of colour pattern, and raise them in another aquarium. The development of all the males will not be visible at the same time and they can be detected gradually during a period of a couple of weeks. Faster developing individuals will colour up first while another males would tend to show signs of colours only after the first dominant males were already removed from the tank. Generally, the distinction between the deep bodied and colourful males and the greyish-brown coloured females do not represent a major problem. In addition, males develop large rounded fins while females, usually, possess hyaline fins. The anal fin of the females is especially diagnostic, having an elongated triangular shape. By observing the shape of the fins, sexes can be separated at a very early stage, even before they would really start to colour up.
When breeding fish that are kept separately by sex, they can be brought together for breeding into a separate tank, which has either peat in a spawning container or the peat can be spread out in the tank, covering the whole bottom. In latter case, the contamination of the spawning medium would be kept at a minimum, as the fish would not be fed in the breeding tank. Females would usually deposit their eggs within a couple of hours, after which the fish can be separated again or replaced with another male and females. When the breeders are fed with varied live food, this operation could be repeated every other day or so.
With most species, the females can be raised together with the males, but with some of the more aggressive species, it is advisable to raise the females separately to give them a better chance to reach a decent size. When the females are then placed again with the males, there will be some fighting but that should settle down soon.
For some aggressive species, such as N. orthonotus, the separation of the sexes and bringing them together for spawning only, might be the most effective way of breeding. Fights might happen amongst them and death periodically occur, as the dominant males continually fight with the less dominant males. If they are left continuously together, they will give a few spawnings before the males eliminate each other. In some N. orthonotus populations, even the females can be so aggressive that they would kill each other until there is one remained.
The most aggressive species is the predatory Nothobranchius ocellatus. As they are very aggressive, they should be brought together in pairs in the breeding tank for a couple of hours only at a time in a separate spawning tank. The eggs of this species are also sensitive to pollution, for which reason it is also advisable to use a separate tank for breeding, where the fish would not be fed.
A somewhat different spawning behaviour can be observed with the species of Aphyobranchius, as the members of this subgenus tend to spawn in middle levels of the water and the very small eggs sink to the substrate. Another species that may also sometimes spawn at mid-water levels is N. fuscotaeniatus. Nevertheless, the Aphyobranchius species tend to carry out their mid-level spawning activity above the peat. Therefore, in most cases, I breed them according to my usual method, having an open spawning container with peat in the tanks, and I can collect good number of eggs when removing the spawning medium.
Storing the Eggs
After a spawning period of one or two weeks, the peat with the container can be removed from the tank and replaced with another portion of peat. The removed peat can be placed in a fine-mesh net and can be squeezed gently to remove excess water. The egg shell is hard and resistant so squeezing gently the peat would not harm the eggs. The peat should keep some level of moisture content but it should not be wet. If necessary, the peat can be placed on a paper towel to air dry for a few hours until it reaches the suitable moisture content. Then the peat containing the eggs can be sealed in a plastic bag and stored. The plastic bag should be labelled, containing the most important information, such as the name of the species, precise location code and date of collecting, as a minimum. The best storage temperature would be around 23-25 °C. When the eggs are stored at much lower temperature, the development time would be considerably longer, while storage at hot conditions accelerates the development. Extreme temperatures in any direction might be harmful for the egg development and, therefore, not recommended.
In some cases it can happen that non-viable eggs turn white and disappear within the first week of storage. Therefore, one or two weeks after collection, the sealed bag with the peat can be re-opened to determine the potential final number of eggs. The fresh and healthy eggs are clear and transparent, usually easy to spot in the brown peat. The eggs can be checked regularly during storage and if we see developed embryos, the hatching process can start.
The development time of the eggs depends on the particular species and is adapted to the different lengths of the dry season in the nature. Species from regions with relatively long dry season have long incubation time, sometimes up to ten months, while species from wetter regions and multiple rainy seasons per year would have shorter development time, sometimes only two months. In addition, incubation time is impacted by the combined effect of several environmental factors, such as temperature, peat moisture content, and amount of available oxygen, among others.
If the eggs are stored in a relatively wet peat, then water will fill out the spare spaces amongst the fibres of the peat. The peat will start to decay and will develop anaerobic conditions, and the oxygen deficient environment will trigger the egg to suspend the development in form of diapausa. This is the case particularly when one is using a fine peat that can compact to a high degree. In some cases, the development of the eggs can take unusually long time when the peat is wet and compact. Drying out the peat a bit would stimulate the eggs for development.
In the case when the peat gets too dry, then there is the risk that the eggs would die off. The moisture content of the peat can be increased by adding some relatively wet peat to the bag containing the eggs and mix them.
Releasing the Oldies
Nothobranchius species grow throughout most of their lives. Due to the specific seasonal conditions of the natural habitats, Nothobranchius species live only a few months in the wild. Under captive conditions their lifespan can be somewhat expanded. However, life expectancy is genetically coded. When kept at relatively lower temperatures, they can live up to one year or a bit more but they remain invariably quite short-lived. After the very dynamic life cycle, the fish arrive at the final stage of their lives. The deterioration of their condition arrives suddenly. The bright colouration of the males fades away, their body bends and they become moody. Females that were full of eggs a short while ago, would get hollow bellies. The irreversible process of vanishing begins.