Nothobranchius Rachovii – Detailed Guide: Care, Diet, and Breeding

Nothobranchius Rachovii – Detailed Guide Care, Diet, and Breeding

Nothobranchius rachovii is the most beautiful and vibrant representative of its genus. However, if you are a beginner aquarist or unfamiliar with this particular species, I would recommend you be extremely cautious and avoid impulsive buys.

On one hand, Nothobranchius rachovii is pretty easy to care for. So, these fish can be easily recommended even for beginners.

At the same time, there are certain aspects that might deter potential buyers. Specifically, these fish have a very short life cycle, and breeding them can be a complex and time-consuming process. Additionally, despite their small size, males of this species are quite territorial.

If you are interested in keeping Nothobranchius rachovii or want to learn more about this species, this care guide will tell you everything you need to know, including their behavior, feeding preferences, ideal tank setups, and how to care for them.

Quick Notes about Nothobranchius Rachovii

Name Nothobranchius rachovii
Other Names Bluefin nothos, African annual killifish, Annual Killifish, Reënboog-kuilvissie,  Blouband-kuilvissie,  Blueband killifish,  Rainbow killifish
Scientific Name Nothobranchius rachovii
Water type Freshwater water
Tank size  10 gallons (~40 liters)
Keeping Easy
Breeding Difficult
Size 1 – 1.7 inches (2.5 – 4.5 cm)
Optimal Temperature 68 – 71°F (20 – 22°С)
Optimal PH 5.5 – 7.0 
Optimal GH 1 – 10 
Dwellers Middle-bottom
Nitrate Less than 100
Diet Omnivore
Temperament Peaceful
Life span up to 1 year
Color Form Blue-orange

Interesting fact: These fish have become a well-established model for aging studies.

Taxonomy of Nothobranchius Rachovii

The genus Nothobranchius consists of about 100 species. These are small fish, typically with standard length ranges from 1.5 – 3 inches (4 – 7.5 cm) species, with striking sexual dichromatism; males are brightly colored while females are mostly dull.

  • Kingdom: Animalia (Animals)
  • Phylum: Chordata (Vertebrates)
  • Class: Actinopterygii (Ray-finned fishes)
  • Order: Cyprinodontiformes (Killifish)
  • Family: Nothobranchiidae (Toothcarp family)
  • Genus: Nothobranchius
  • Species: Rachovii

Etymology of Nothobranchius Rachovii

The genus name “Nothobranchius” is derived from the Greek words “Nothos”, meaning “False” and “Brangchia” meaning “Gill”.

The species name “Rachovii” is a homage to the German aquarist Arthur Rachow (1884–1960), who donated a number of fish specimens to the Museum für Naturkunde.

Distribution of Nothobranchius Rachovii

Nothobranchius Rachovii – Detailed Guide Care, Diet, and Breeding destributionThis species is endemic to Mozambique. It inhabits the lower Zambezi and lower Pungwe River systems in Mozambique.

Habitat of Nothobranchius Rachovii

The natural habitats of Nothobranchius rachovii are seasonal pools and temporary water bodies where the water dries up annually.

Its life cycle is closely tied to the availability of water in these habitats produced by seasonal rains, and its rapid and short active life commences when rains fill the pool.

Description of Nothobranchius Rachovii

Nothobranchius rachovii is a small freshwater fish. The typical adult size ranges from 1 to 1.7 inches (2.5 to 4.5 centimeters) in length.

According to some studies, there are reports of individuals reaching sizes of up to 3.5 inches (8.0 cm). However, in my personal experience, I have never seen them grow that big.

Nothobranchius Rachovii – Detailed Guide Care, Diet, and Breeding sexingDistinguishing characteristics of Nothobranchius rachovii:

  • Body shape.The body is long and compressed laterally, with a dorsal profile that is slightly concave on the head and convex from the nape to the end of the dorsal fin.
  • Head. This species has a pointed snout, and a terminal mouth that is slightly directed upward.The lower jaw protrudes forward. In the front row, only a few teeth are larger, massive, conical, and curved backward. Behind this row, all the teeth are arranged in a wide row, and in the very last row, the teeth are not large.
  • Eyes. The eyes are medium-sized. The eye diameter is 3 1/3 – 3 1/2 times smaller than the head and 1 1/2 times smaller than the interorbital distance.
  • Сoloration and pattern. The fish has orange and black terminal stripes on its caudal fin.

Males exhibit a vibrant color pattern featuring alternating light blue and orange-red stripes on the body and fins, orange-red head, and orange subterminal and black terminal bands in the caudal fin. The specific coloration, particularly in the head area, may vary based on factors such as aquarium conditions and water quality.

Females have an olive grey-brown coloration. The frontal scales on the flanks are iridescent light blue to silvery. All fins are colorless.

  • Fins. It has 15-17 soft dorsal fin rays and 15-18 soft anal fin rays. This species does not have a hard ray in the dorsal and anal fins. Pelvic fins are short, not reaching the origin of the anal fin; pectoral fins reach to origin of the pelvic fins. All unpaired fins are rounded,
  • Scales. The scale number varies from 26 to 28.

Lifespan of Nothobranchius Rachovii

Nothobranchius rachovii is an annual species. In their natural habitat, these fish typically have an average lifespan of 6-8 months.

In aquariums, with appropriate conditions, these fish can live for around 1 year.

According to the study, the maximum survival is about 15 months. It was observed that during the last aging period, fish suffer changes in their morphology as spine curvature, body coloration loss, and progressive deterioration of the fins, especially the caudal fin. Additionally, it was also noticed that the aged fish (8 months) compared with young fish (3 months) showed signs of reduced movement.

Their lifespan greatly depends on the temperature as well. Experiments showed that the survival of 4-month old fish follows a similar trend:

  • 90 days at 68°F (20°C),
  • 60 days at 77°F (25°C),
  • 33 days at 86°F (30°C).

Typical Behavior of Nothobranchius Rachovii

Temper:

Females of this species are absolutely trouble-free; they are very peaceful and harmless. However, Nothobranchius rachovii is mostly chosen for its brightly colored males. So, when it comes to temperament, it can match their vibrant coloring.

Besides intraspecific aggression toward subordinate males, dominant males may also show aggression not only towards females but also towards other fish species, even if they are slightly larger.

Over time, if there are multiple males in the aquarium, each will claim and guard its territory from others.

Sociality:

It’s better to keep Nothobranchius in nest groups, with two to three females for one male.

To mitigate aggression, it is recommended to raise and breed them in groups, comprising 5-6 males and 10-12 females, without separating them.

Isolating a male from the group, even for just one week, can lead to issues.

Keeping them in groups from the beginning helps distribute aggression evenly, and it also offers the advantage of a larger genetic pool. However, this approach requires larger aquariums.

Activity:

This diurnal species is known for its lively and active behavior in the aquarium. They are constantly on the move, exploring their environment with swift and agile movements.

Their activity level is particularly notable during feeding times, when they eagerly chase and consume food.

Interesting fact: Nothobranchius rachovii exhibits sleep-like states characterized by short periods of inactivity, floating near the tank surface with no pectoral fin movements during the nocturnal phase. Sleep is also identified when locomotor activity drops below the 33rd percentile.

Placement in Tank:

Nothobranchius rachovii spends most of the time in the open, often checking the bottom of the tank and hovering in midwater.

They enjoy exploring their environment and are particularly fond of areas with dense vegetation or places to hide.

Features:

  • Social: Yes
  • Activity: High
  • Placement: Middle and bottom dwellers
  • Peaceful: Conditionally
  • Nippers: No
  • Jumpers: Yes

Feeding Nothobranchius Rachovii

Analysis of stomach contents revealed that Nothobranchius rachovii is generalist, primarily consuming aquatic invertebrates (such as Cladocera, Copepoda, Ostracoda, and Conchostraca), and Mosquito larvae.

In aquariums, these fish are easy to feed as they are not picky eaters. They can be provided with a diverse range of frozen or live foods, including:

Large worms (grindal worms, bloodworms, blackworms, etc.) should be chopped into small pieces and flake food should be crumbled.

How to Feed Nothobranchius Rachovii?

  • They are diurnal animals; these fish should be fed during the day.
  • Make sure it is mostly a protein-based diet.
  • They are prone to overeating if given too much (follow a “5-minute rule”).

Features:

  • Diet Type: Omnivore
  • Food Preference: Protein-rich
  • Feeding Frequency: Daily

How Often to Feed Nothobranchius Rachovii?

Ideally, they should be fed twice per day (in the morning and the evening).

Is Nothobranchius Rachovii Plants Safe?

Yes, Nothobranchius rachovii are plant safe. They do not eat live plants at all.

Even more, planted tanks are highly recommended for them since it help to reduce potential aggression.

Keeping and Housing Nothobranchius Rachovii

Nothobranchius Rachovii – Detailed Guide Care, Diet, and BreedingWhile these fish are resilient, considering their natural habitat in temporary pools and water-filled depressions, we still need to meet their specific requirements for optimal health and breeding.

Ensure your tank is properly cycled before introducing it. Regularly test water quality with a kit to monitor ideal conditions.

Tank size:

The recommended tank size for this species is 10 gallons (40 liters) for 1 male and 2 – 3 females. This gives them adequate space for swimming and hiding.

For two breeding groups (2 males and 6 females), a 15-gallon aquarium would be necessary as the males will establish and defend their territories.

Important: Nothobranchius rachovii are good jumpers. Therefore, to prevent it from happening, there are a few things you can do:

  • get a lid for the tank,
  • lower the water level,
  • keep floating plants,
  • do not stress your fish.

Water Parameters:

Temperature: In their natural habitat, the temperature is around 68 to 76°F (20°C to 24°C), but it can also rise up to 86°F (30°C) during the dry season.

However, since high temperatures significantly shorten their lifespan (see above), it’s better to keep them at 68 to 71°F (20 – 22°C).

pH: The ideal pH range is 5.5 to 7.0.

Hardness: The recommended general hardness range for these fish is 1 to 10 GH. The recommended carbonate hardness range is 1 to 8 KH. Although this species can adapt even to harder water, eventually, it will reduce its lifespan as well.

Water Flow:

In the natural ecosystem, these fish inhabit shallow waters where the current is absent or very slow-moving.

Therefore, stagnant water or very slow water currents are recommended for tanks housing this species.

Experiments showed that Nothobranchius rachovii age faster under stress due to continuous water recirculation.

Filtration:

Filtration will be crucial as it partly affects the water flow in the aquarium. Therefore, it is recommended to choose filters with minimal flow, such as sponge filtration.

Lighting:

Nothobranchius rachovii does not like bright light. These fish enjoy subdued lighting.

However, if you decide to keep these fish in planted tanks, lighting should be adapted to the needs of plants.

Related articles:

Substrate:

No special requirements.

Tip: Although you can choose any substrate for the tank, it is better to have a dark color so that the fish looks more contrasting against its background.

Plants and Decorations:

Nothobranchius rachovii requires plenty of dark hiding spots using plants, rocks, stones, driftwood, coconuts, cork bark pieces, leaves, PVC pipes, and other decorations to enrich their environment. 

Decorations provide hiding places (shelter and protection) and minimize their stress, especially, if there are several males.

Tip: Some aquarists strategically place items like coconuts in various locations within the aquarium. This is done so that males can use them as shelters, ultimately establishing a central point from which they can control their territory.

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Breeding Nothobranchius Rachovii

The breeding process of Nothobranchius rachovii is directly linked to its annual life cycle. In their natural environment, these fish inhabit water bodies that completely dry up, leading to the demise of all the fish.

Therefore, these fish lay their eggs in mud for the next generation to be born and survive drought until the onset of the rainy season.

In aquariums, we have to completely replicate this process as well.

Maturity:

Depending on the temperature, Nothobranchius rachovii can reach sexual maturity anywhere from 3 weeks to 2 months old.

 Sexing:

In this species, adult males are larger. Additionally, the adult males and females are easy to distinguish by color, they are much more colorful compared to drab females.

Interesting fact: Scientists noticed that removing males from a population leads to larger female fish that produce fewer eggs. They suggest that the absence of sexual stimuli reduces egg production, allowing females to save energy for growth.

Spawning:

In Nothobranchius rachovii, spawning is portioned and prolonged, with several small batches of eggs laid daily.

During courtship rituals, the male aims to press the female to the bottom, and a distinctive feature of this species is the male’s “vertical” posture with its head upward. During courtship, the male makes sudden movements, often lowering his lower lip and holding his head at an angle of about 45°.

Fecundity:

According to the study, female Nothobranchius rachovii have the capacity to lay an impressive 20–30 eggs in each clutch per day. Despite this potential, the average number typically ranges from 4 to 10.

Eggs:

The fertilized eggs have characteristics of adhesive, spherical, yellowish, and demersal, and had a large oil droplet. The size of the fertilized eggs is about 0.039 inches (0.97±0.03 mm).

The oil droplet in fertilized egg is utilized as a food source. The egg envelope consists of two distinct layers that allows them to survive dry periods.

Embryos:

Embryos enter into a diapause state for 6 – 9 months. Their development slows down until the new rainy season arrives.

Note: Nothobranchius rachovii relies on diapause, as their eggs will not survive if fully submerged in water for more than a few weeks.

Fry:

After hatching, the fry grow and mature extremely fast.  In the natural environment, nearly 90% of the embryos and fry survive and reach adulthood.

For example, the average size of male fish at:

  • 1-month old is 2.3 ± 0.15 cm (1 inch) in length
  • 4-month old is 3.7 ± 0.22 cm (1.5 inches) in length
  • 7-month-old is 4.3 ± 0.35 cm (1.7 inches) in length

Breeding Method:

  1. To initiate breeding:
  • Put a male and a female into the breeding tank.
  • provide peat or coconut fiber as a substrate,
  • condition them by giving lots of live food,
  • increase the temperature to 77 – 79°F (25 – 26°C),
  • lower the water level a bit.

Tips: Instead of adding the substrate directly into the aquarium, you can take a small plastic jar and fill it with the substrate (layer up to 1 inch (2.5 cm)).

Some experienced aquarists also recommend boiling peat for 3-5 minutes before use. It makes the peat clean but at the same time preserves the significant acidic reaction of the peat. If you boil peat for too long, almost all acids break down, causing the peat to lose the ability to kill harmful bacteria that can destroy the eggs of fish spawning in the bottom substrate.

During spawning, the female deposits eggs directly into the substrate, and the male fertilizes them.

  1. After a few days of egg laying, return the breeders to the main tank. Females, due to their very fast metabolism often consume eggs.
  2. If you use a container with substrate, you can simply take it out of the water. Otherwise, you’ll need to completely dry out the aquarium to collect the substrate with eggs.
  3. Press the substrate slightly to remove excess water and let it dry.
Important: Dry the substrate until it easily crumbles in your hands while still slightly moist. It is crucial not to overdry the substrate, as it can lead to the dehydration of the eggs and hinder their development. At the same time, insufficiently dried substrate can cause developmental delays.
  1. Place it in a plastic bag, sealing it so that 3/4 of it is filled with air.
  2. The incubation period usually varies from 6 to 9 months. During all this time, you need to store the substrate at 21-25°C in a dark place. Once a month, ventilate it, and check the eggs. If the peat is too dry, moisten it.
  3. During incubation, our task is to monitor the development of the embryo’s eyes, and once they are formed, it’s time to add water.
  4. Put the substrate back into the water. Keep water soft (4 – 8 GH) and acidic (6.0 – 6.5 pH).
  5. Once the fry hatch, feed them with infusoria. Make sure that fry always have food.

Keep in mind that Nothobranchius rachovii eggs never develop all at once. This is a defense mechanism against so-called false rain, allowing the species to survive in nature. Therefore, the hatching of fry occurs in batches.

Do not forget to maintain water quality. Regularly remove waste and leftovers in the tank. You can also add a few snails as a clean up crew.

Nothobranchius Rachovii and Suitable Tankmates

When selecting tankmates for Nothobranchius rachovii, it is crucial to consider their relatively peaceful yet territorial nature. Therefore, ideally, a species-only tank is recommended.

Fish:

If you still decide to keep this species in community tanks, its tank mates should be all small fish species that are not big enough to eat or harass them. Ideally, you need to choose species that prefer (or can tolerate) soft and slightly acidic aquarium water, such as:

Shrimp:

It is possible to keep Nothobranchius rachovii with dwarf shrimp to some degree. These fish will not be a threat to adults or even juvenile shrimp.

However, newly-hatched shrimp are tiny enough (0.03 inches or 2 mm) to fit in their mouth. So, they will certainly snack on them from time to time.

Snails:

They are compatible with any freshwater snail

Avoid:

  • Large and/or aggressive, and/or boisterous fishes.
  • Keep them away from all types of crayfish and most types of freshwater crabs. 

Related article:

In Conclusion

Nothobranchius rachovii is a fascinating and beautiful aquarium fish that is relatively easy to care for in a species tank, making it suitable for beginners.

However, we need to always attention to the males’ territorial behavior and the challenges of breeding, not just their care.

References:

  1. Shidlovskiy, K.M., B.R. Watters and R.H. Wildekamp, 2010. Notes on the annual killifish species Nothobranchius rachovii(Cyprinodontiformes; Nothobranchiidae) with the description of two new species. Zootaxa 2724:37-57
  2. Hsu, Chin‐Yuan, and Ya‐Chi Chiu. “Ambient temperature influences aging in an annual fish (Nothobranchius rachovii).” Aging Cell8, no. 6 (2009): 726-737.
  3. Kwon, Ohyun, Joon Hyung Sohn, Dong Yong Chung, Eun Jin Kim, and Dong Heui Kim. “Comparative ultrastructures of the fertilized egg envelopes in Nothobranchius foerschi and Nothobranchius rachovii, Nothobranchiidae, teleostei.” (2017): 70-74.
  4. Lucas-Sánchez, Alejandro, Pedro F. Almaida-Pagán, Douglas R. Tocher, Pilar Mendiola, and Jorge de Costa. “Age-related changes in mitochondrial membrane composition of Nothobranchius rachovii.” Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences69, no. 2 (2014): 142-151.
  5. Polačik, M., and M. Reichard. “Diet overlap among three sympatric African annual killifish species Nothobranchius spp. from Mozambique.” Journal of Fish Biology77, no. 3 (2010): 754-768.
  6. Radkhah, Ali Reza, Soheil Eagderi, and Esmaeil Sadeghinejad Masouleh. “Investigation of biological and ecological characteristics of Bluefin Notho Nothobranchius rachovii Ahl, 1926 (Cyprinodontiformes: Nothobranchiidae) as one of the freshwater aquarium fish: A review.” Journal of Ornamental Aquatics9, no. 3 (2022): 21-30.
  7. Herrera, Michael, and Pudur Jagadeeswaran. “Annual fish as a genetic model for aging.” The Journals of Gerontology Series A: Biological Sciences and Medical Sciences59, no. 2 (2004): B101-B107.
  8. Lucas-Sánchez, Alejandro, Antonio Martinez-Nicolas, Juan Antonio Madrid, Pedro Francisco Almaida-Pagán, Pilar Mendiola, and Jorge de Costa. “Circadian activity rhythms during the last days of Nothobranchius rachovii’s life: a descriptive model of circadian system breakdown.” Chronobiology international32, no. 3 (2015): 395-404.

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