Sundadanio Axelrodi 101: The Ultimate Care Guide

Sundadanio Axelrodi is an intriguing fish species that captivates aquarists with its stunning iridescent blue color. 

Fondly referred to as the Blue Neon Rasbora, this petite freshwater creature hails from the tranquil waterways of Southeast Asia. 

Their vibrant, shimmering blue stripes coupled with their peaceful nature make them a spectacular addition to any home aquarium. 

In this guide, I’ll walk you step by step through everything you need to know about keeping Sundadanio Axelrodi – from understanding their history and natural behavior to detailing their specific needs in terms of diet, habitat, and care.

Sundadanio Axelrodi Summary

Common NamesBlue Neon Rasbora, Neon Blue Rasbora, Axelrod’s Rasbora
Scientific NameSundadanio axelrodi
SpeciesS. axelrodi
ColorNeon blue or green
SizeUp to 2 cm (0.8 inches)
Lifespan4-5 years
pH Level5.5-7.0
Water Temperature73-82°F (23-28°C)
Water Hardness1-12 dKH (soft to medium hardness)
Water TypeFreshwater
Minimum Tank Size10 gallons
Community TankYes, best kept in a school of at least 10. Compatible with other peaceful, small fish species.
Care LevelEasy, suitable for beginners
CompatibilityCompatible with other small, peaceful fish species. Avoid keeping with larger or aggressive fish species.

Sundadanio Axelrodi History

Sundadanio Axelrodi, commonly known as the Blue Neon Rasbora, is a species of tropical fish named in honor of the famous ichthyologist, publisher, and tropical fish enthusiast, Dr. Herbert R. Axelrod. 

Axelrod has made significant contributions to the field of ichthyology, and the naming of this species is a recognition of his work.

The Sundadanio Axelrodi is part of the Cyprinidae family, the largest family of freshwater fishes in the world. 

This family includes other popular aquarium species such as danios, minnows, and barbs.

First discovered in the mid-20th century, Sundadanio Axelrodi was quickly adopted into the aquarium trade due to its striking neon coloration and peaceful behavior. 

As more hobbyists have started keeping tropical fish, Sundadanio Axelrodi has gained popularity due to its hardy nature, vibrant colors, and peaceful demeanor. 

These features, coupled with its relatively easy care, make the species an attractive choice for both beginner and experienced aquarists.

And despite its size, this fish plays a significant role in its natural ecosystem by contributing to the biocontrol of smaller pests and serving as a food source for larger species. 

Over time, through careful breeding practices in both farms and home aquariums, the vibrant colors of the Sundadanio Axelrodi have been enhanced, leading to the stunning variety of hues we see today.

Sundadanio Axelrodi Behavior

Originating from the blackwater streams of Borneo and Sumatra, these tiny but vibrant fish have adapted behaviors that enable them to navigate the challenges of their environment effectively.

One of the key characteristics of Sundadanio Axelrodi is their schooling behavior. 

As is common among smaller fish species, the Blue Neon Rasboras band together in groups, forming a school. 

This instinctual survival strategy serves multiple purposes. For one, when seen in a large group, these small fish give the impression of a much larger creature, which can act as a deterrent to potential predators. 

Furthermore, the unity of a school provides a sense of security to the individual fish. 

This schooling nature reduces stress, fostering a conducive environment for the fish to exhibit normal feeding and breeding behaviors.

However, the social aspect of Sundadanio Axelrodi doesn’t end with their tendency to school. In their natural habitat, they’re typically shy and reclusive. 

To protect themselves from predators, these fish prefer to take cover amongst the aquatic flora and fallen leaves and branches during the day. 

This behavioral attribute is primarily influenced by the low-light conditions that are characteristic of blackwater streams. 

These timid creatures emerge from their hiding places and become most active at dawn and dusk, a phenomenon known as crepuscular activity. 

This rhythm allows them to evade predators that typically hunt during the day or night, further enhancing their survival strategy.

With regard to their dietary habits, Sundadanio Axelrodi maintains an omnivorous diet in the wild. 

They feed on a diverse menu, including small invertebrates, insect larvae, and various types of algae and plant matter. 

The role they play in the food chain is not insignificant; by controlling the population of small pests, these fish contribute to the ecological balance of their habitat.

Their reproductive behavior is another captivating aspect of their life in the wild. 

Unlike many other species that carefully choose and prepare a site for egg-laying, these fish scatter their eggs randomly among plant leaves and the substrate. 

Following the female as she scatters its eggs, the male fertilizes them. 

This unique reproductive strategy increases the chances of survival for their offspring. 

The scattered nature of the eggs makes it harder for predators to find and consume all of them at once.

Sundadanio Axelrodi Origin & Habitat

The Sundadanio Axelrodi is a tropical freshwater fish that hails from Southeast Asia. 

Its specific geographic distribution includes the densely forested regions of Borneo and Sumatra, two islands known for their rich biodiversity and unique aquatic ecosystems.

Within these regions, Sundadanio Axelrodi dwells in blackwater streams. These habitats are known as “blackwater” due to the heavy presence of decomposing organic matter like leaves, bark, and roots. 

This material releases tannins into the water, lending it a tea-like, dark amber color that becomes almost black when viewed from a certain depth or angle. 

Blackwater environments are typically low in mineral content but highly acidic due to the organic material decay, thus creating very specific living conditions for their aquatic residents.

Sundadanio Axelrodi has adapted brilliantly to these distinctive blackwater conditions.

 In the wild, they thrive in slow-moving or standing bodies of water, where the dense canopy of the rainforest provides a filtered, subdued light setting. 

These conditions contribute to the relatively cooler water temperatures, generally ranging between 73-82°F (23-28°C), preferred by this species.

Moreover, the floor of these streams is usually carpeted with a thick layer of fallen leaves, twigs, and peat, providing plenty of hiding spots for these timid, small creatures. 

The water’s acidity level, which varies from slightly acidic to neutral (pH 5.5-7.0), together with the soft to medium hardness (1-12 dKH), supports the health and vibrancy of Sundadanio Axelrodi.

What Are the Features of Sundadanio Axelrodi?

1. Appearance

As the common name suggests, the most striking feature of Sundadanio Axelrodi is its neon-like coloration. 

Depending on their mood, lighting conditions, and general health, these fish can exhibit a stunning palette ranging from iridescent blue to green hues. 

Some specimens also showcase a delightful mix of red, pink, and silver accents, especially around the belly and the base of their fins.

When observed under good light, their body appears to shimmer, creating a mesmerizing, glowing effect that justifies their reputation as one of the most visually appealing nano fish in the aquarium trade. 

Their vibrant coloration is not merely a beauty feature but also an adaptive mechanism for survival, enabling them to blend with the dark, tannin-stained waters of their native habitats.

In terms of physical form, Sundadanio Axelrodi possesses a slim, elongated body typical of many small schooling fish. 

This streamlined shape allows them to navigate their surroundings with ease, especially during rapid escapes from perceived threats.

It also features a pair of proportionally large eyes relative to their body size, a common trait among species living in darker or dimly lit waters. 

These large eyes help them navigate their environment and locate food sources effectively.

2. Body Size

Fully grown adult Sundadanio Axelrodi typically measure just 2 cm (approximately 0.8 inches) in total length, including the tail.

Despite their tiny stature, they command attention with their iridescent hues and schooling behavior, making them the perfect addition to a peaceful community tank setup.

Sundadanio Axelrodi Lifespan

Sundadanio Axelrodi typically enjoys a lifespan ranging from 3 to 5 years in well-maintained aquarium conditions. 

Sundadanio Axelrodi Life Cycle

1. Egg Stage

The life cycle of Sundadanio Axelrodi begins as an egg, which is laid by the female after a courtship display by the male. 

The female scatters her eggs amongst fine-leaved plants or on the substrate. 

This stage is quite delicate as the eggs are vulnerable to predation, even from adult Rasboras themselves. 

Hence, you should separate the eggs into different tanks to ensure their safety. The eggs are tiny and transparent, making them difficult to spot.

2. Fry Stage

After about 24 to 36 hours of laying, the eggs hatch into the next stage of the life cycle known as the “fry” stage. 

Sundadanio Axelrodi fry are incredibly small and will initially feed on the yolk sac attached to their bodies. 

After this yolk sac is consumed, which usually takes a couple of days, they begin free swimming and start feeding on infusoria or other micro-foods suitable for their tiny mouths. 

At this stage, the fry are highly susceptible to water conditions and require stable parameters to ensure their survival.

3. Juvenile Stage

The fry gradually grow into the juvenile stage, which is marked by the development of more distinct features and colorations. 

During this stage, the young Sundadanio Axelrodi start to resemble their adult counterparts, although they are still smaller and less brightly colored. 

Their diet also begins to expand to include finely ground flake food or tiny live foods like baby brine shrimp.

4. Adult Stage

After several weeks to a few months, depending on the specific conditions and care level, the juveniles mature into adult Sundadanio Axelrodi. 

Reaching their maximum size of around 2 cm, the adults now display the full, stunning coloration that makes this species so desirable. 

At this stage, their diet is diversified to include a variety of flake foods, live foods, and frozen foods. 

Adult Blue Neon Rasboras are ready to reproduce at this stage, thus completing the cycle and starting it anew with their offspring.

Is Sundadanio Axelrodi Hardy?

Despite their delicate appearance and small size, Sundadanio Axelrodi is a relatively hardy fish that can adapt well to a range of conditions in a well-maintained aquarium. 

They have the capacity to tolerate a variety of water parameters as long as sudden changes are avoided, which can stress them and potentially lead to health problems.

How to Care for Sundadanio Axelrodi?

a.Water Requirements

1. Water Quality

One of the crucial elements to monitor in their habitat is water quality. High-quality water is the backbone of a healthy aquarium, playing a pivotal role in the well-being of its inhabitants.

The significance of regular water changes in maintaining water quality cannot be overstated. 

A common guideline is to conduct a 25% water change weekly. 

This not only helps to keep the water parameters stable but also helps to remove toxins that can accumulate over time. 

An important factor in water quality is also the levels of toxins in the tank. 

Fish excrete waste, which, if not properly managed, can increase the levels of ammonia and nitrites in the water. 

Both these chemicals are highly toxic to fish and can lead to various health issues, even fatalities. 

Ammonia is produced when fish excrete waste, leftover food decomposes, or when a plant dies and starts to decay. 

Beneficial bacteria in the tank usually convert this ammonia into nitrites and then into less harmful nitrates. 

However, if these bacteria are not present in adequate numbers, ammonia levels can rise, putting your fish at risk.

To keep track of these toxin levels and ensure they are within safe parameters, you should test the water regularly. 

I prefer the API Master Test Kit. This kit is comprehensive, reliable, and quite easy to use. 

It includes tests for ammonia, nitrite, nitrate, and pH levels, covering all the essential parameters you need to monitor in an aquarium setting.

To use this kit, just collect a small sample of aquarium water in the provided test tubes, add the appropriate reagents for each parameter, shake gently to mix, and then compare the resulting color against the included color chart. 

This method gives you a clear understanding of the current water conditions in your tank and whether any immediate action is required.

2. Water Temperature

These tropical fish, native to the warm waters of Borneo and Sumatra, thrive in stable water temperatures ranging from 73-82°F (23-28°C)

The importance of maintaining this temperature range stems from the fact that the metabolic functions of fish are highly influenced by the temperature of their surroundings.

If the water is too cool, their metabolism slows, resulting in lethargy and reduced immune function. 

And if the temperature climbs too high, their metabolism can speed up excessively, leading to stress and potentially shorter lifespan.

So, you can use an aquarium heater to maintain stable water temperatures, especially in cooler climates or air-conditioned environments. 

Heaters with thermostats also allow for precise temperature control and maintenance. 

Importantly, you should place the heater and thermometer at opposite ends of the tank to ensure a more uniform temperature distribution. 

3. pH Level

The pH level in an aquarium represents how acidic or alkaline the water is, a factor that can significantly influence the health of your Sundadanio Axelrodi. 

The pH scale ranges from 0 to 14, where a value of 7 is neutral. Anything below 7 is considered acidic, while values above 7 are alkaline.

Sundadanio Axelrodi, hailing from soft, slightly acidic waters, prefers a pH range of 5.5 to 7

It’s important to note that sudden changes in pH can be extremely stressful to fish, often more so than the actual pH value. 

Hence, stability is key when it comes to pH in an aquarium. Regularly testing the water will help monitor the pH levels and make sure they stay consistent.

A reliable testing kit like the API pH Test Kit can be a useful tool to keep an eye on your aquarium’s pH levels. 

This kit measures a wide range of pH, allowing aquarists to identify the pH level within no time.

If the pH levels do fluctuate beyond the ideal range, you should identify the cause. 

Overfeeding, overstocking, decaying plant matter, or inadequate water changes could all contribute to a shift in pH. 

Once the underlying issue is addressed, products like Seachem Acid Buffer or Alkaline Buffer can help adjust the pH to a safer range.

4. Water Hardness

Water hardness refers to the concentration of mineral ions, particularly calcium and magnesium, present in the water. 

Sundadanio Axelrodi is naturally accustomed to soft water environments, favoring a water hardness range between 1 and 12 dGH (degrees General Hardness). 

In their natural habitat, they’re typically found in waters with lower mineral content, often tinted with humic substances from decaying plant material. This is why they thrive best in soft water conditions in an aquarium.

Testing the water hardness regularly is essential in an aquarium housing Sundadanio Axelrodi. 

A test kit such as the API GH & KH Test Kit can be used to determine the General Hardness (GH) and Carbonate Hardness (KH) of your tank’s water. 

This test kit is straightforward to use and can help you maintain the correct water hardness levels.

If you find that your tap water is too hard, there are ways to soften it before adding it to the aquarium. 

You can add peat moss to the filter, which releases tannins that soften the water. 

Alternatively, Reverse Osmosis (RO) water can be used, either alone or mixed with tap water, to achieve the right hardness levels.

b.Tank Requirements

1. Tank Size

While they are small fish, usually not exceeding 2 centimeters in length, their need for space should not be underestimated.

Sundadanio Axelrodi is schooling fish, which means they feel safest and most comfortable when in a group of their own kind. 

A minimum group of 6 to 8 is ideal, although larger schools are even better. 

So, a 10-gallon tank is often the absolute minimum for a small group of Sundadanio Axelrodi. 

However, given their active nature and schooling behavior, a larger tank would be more suitable. 

A 20-gallon tank, or even larger if space permits would give them more room to swim and display their natural behaviors.

Apart from allowing enough space for the fish to move, a larger tank also helps maintain stable water parameters, which is essential for the health of Sundadanio Axelrodi. 

When selecting a tank, consider its dimensions too. 

These guys prefer longer tanks, which provide more swimming space. A tank with a larger footprint is usually better than a taller one of the same volume.

2. Decorations

Sundadanio Axelrodi is native to slow-moving streams and tributaries, which are usually rich in plant life, driftwood, and leaf litter. 

To mimic these conditions, the first consideration is to include live plants in your tank setup. These tiny fish feel secure in densely planted aquariums. 

Moreover, the presence of live plants also contributes to maintaining water quality, as plants help absorb nitrates. 

Easy-to-care-for plants such as Java Moss, Java Fern, and Anubias are excellent choices. 

Adding floating plants can also provide shading and further enhance the sense of security for these fish.

In addition to live plants, incorporating elements like driftwood and rocks enhances the aesthetics while offering practical benefits. 

These natural elements serve as additional hiding places and create a sense of a more organic habitat. 

Strategically arranging driftwood and rocks to create caves or overhangs adds an extra layer of exploration and refuge for the fish.

To bring the environment even closer to their natural habitat, consider adding leaf litter. 

Indian Almond Leaves, or Catappa Leaves, can replicate the tannin-stained waters Sundadanio Axelrodi is used to. 

Additionally, these leaves offer antibacterial properties that can contribute to a healthier aquarium environment.

The choice of the substrate also impacts the overall feel of the tank. 

Sundadanio Axelrodi’s vibrant colors contrast beautifully with a dark substrate, such as fine river sand or dark aquarium gravel. 

This not only adds to the visual appeal but also closely mirrors the substrates found in their natural habitats.

However, while decorating, it’s important to ensure there’s enough open space for these active swimmers. 

You should also avoid any sharp-edged decorations that could harm the fish. 

3. Lighting

When considering the lighting for your Sundadanio Axelrodi aquarium, it’s important to remember that these fish are naturally found in shaded, canopy-covered streams. 

Thus, they prefer dimly lit conditions rather than bright, direct light.

These fish, like many fish species, are sensitive to abrupt changes in light. 

Rapid transitions from darkness to bright light can cause stress and even frighten these small creatures. 

This is why you should use a gradual lighting system or make sure that the room has ambient light before turning on the aquarium light.

The choice of lighting can also influence the growth of live plants in your aquarium. 

Most aquarium plants require a decent amount of light to thrive, although the exact requirements vary from species to species. 

So, when choosing a light, consider both the needs of your Sundadanio Axelrodi and the plants you intend to keep.

LED lights are a popular choice for aquariums, as they are energy-efficient and you can adjust them to create the desired lighting effect. 

Some advanced LED lighting systems even come with a timer or a dimmer to allow for a more gradual transition from darkness to light and vice versa.

They also require a consistent day-night cycle to regulate their internal rhythms. 

A good rule of thumb is to provide around 8 to 10 hours of light per day and ensure your fish have a period of complete darkness for rest.

Sundadanio Axelrodi Compatibility

The Sundadanio Axelrodi is a peaceful fish species that makes an excellent addition to community aquariums. 

Their peace-loving nature, combined with their schooling behavior, creates an attractive visual spectacle without disturbing the tranquility of the tank.

However, their compatibility with other tank mates requires careful consideration due to their small size. 

Larger or more aggressive species can view the diminutive Sundadanio Axelrodi as potential prey or competition, leading to stress or harm. 

Hence, it is best to choose tank mates that are similar in size and temperament.

Here is a detailed breakdown of good and bad tank mates for these guys:

Good Tank MatesBad Tank Mates
Other RasborasLarge Catfish
DaniosBetta Fish
GuppiesOther Fin Nippers
Corydoras CatfishLarge, Aggressive Species
Otocinclus Catfish

Sundadanio Axelrodi Diet & Feeding

In the wild, Sundadanio Axelrodi, are micro-predators, primarily feeding on small invertebrates, insects, and zooplankton. 

They consume a range of minute aquatic life that inhabits the blackwater streams of their native habitats. 

In captivity, replicating this diverse diet as closely as possible is vital to ensure their optimal health and well-being. You should feed Sundadanio Axelrodi a varied diet that includes:

  • High-quality flake food
  • Micro-pellets
  • Daphnia
  • Brine shrimp
  • Microworms
  • Bloodworms
  • Vegetable matter and algae-based foods

Here’s a sample feeding schedule you can use as a guideline:

MondayHigh-Quality Flake FoodBrine Shrimp
TuesdayMicro PelletsFlake Food
WednesdayDaphniaMicro Pellets
ThursdayFlake FoodBrine Shrimp
FridayMicro PelletsFlake Food
SaturdayDaphniaMicro Pellets
SundayFlake FoodBloodworms

Sundadanio Axelrodi Breeding

Breeding Sundadanio Axelrodi presents an exciting opportunity for aquarists to observe the full lifecycle of these captivating fish. 

These diminutive species are egg scatterers, indiscriminately spreading their eggs over the substrate or among aquatic plants. 

While parental care is not a trait of the Sundadanio Axelrodi, with the right tank conditions, they breed readily in captivity.

To encourage breeding, it’s crucial to set up a suitable environment that closely mimics their natural habitats. 

The Sundadanio Axelrodi prefer soft, slightly acidic water with temperatures ranging from 78 to 82°F (25.5 to 27.7°C) for their spawning process. 

If feasible, a dedicated breeding tank can be advantageous as it allows for optimal control of conditions and ensures protection for both eggs and fish from potential predators. 

Planting the tank densely or incorporating spawning mops provides cover and ideal locations for the fish to scatter their eggs.

In terms of selecting pairs for breeding, maintaining a school of at least 8-10 Sundadanio Axelrodi enhances the chances of natural pair formation. 

As the school mingles and interacts, pairs will form over time. 

The males, being more vibrant in color and slimmer, are relatively easy to distinguish from the females, who present a plumper appearance, especially noticeable when carrying eggs.

Once pairs have formed, the next step is to condition them for breeding. 

Providing a diet rich in live or frozen foods is key in this phase. 

Foods high in protein also stimulate egg production in females and trigger spawning behaviors in males, preparing them for the reproductive process.

The spawning process usually kicks off in the early morning. 

Males are known to exhibit a dance-like display to entice females to the chosen spawning site. 

In response, the female scatters its eggs, which the male then fertilizes. 

Following spawning, it’s advisable to remove the parent fish to prevent any predation on the eggs, as Sundadanio Axelrodi lacks parental instincts.

The final phase of the breeding journey involves raising the fry. 

Eggs hatch between 24 to 36 hours, and the fry becomes free-swimming within 3-4 days

Initially, feeding them infusoria or commercially available fry food nourishes their tiny bodies. 

As they grow, transitioning to finely crushed flake food and, eventually, to the regular diet of adult Sundadanio Axelrodi ensures their optimal growth.

Sundadanio Axelrodi Common Diseases

Sundadanio Axelrodi, like all fish species, are susceptible to various diseases, particularly when kept in suboptimal conditions. 

Some of the common diseases that can affect them include:

IchWhite spots on body and gills, lethargy, loss of appetite, increased gill movementParasite (Ichthyophthirius multifiliis)Increase water temperature and use ich treatment medicationMaintain high water quality, quarantine new fish
Fin rotFraying or disintegration of finsBacterial infection, often due to poor water conditionsImprove water conditions, use the antibiotic or antibacterial medicationRegular water changes, maintaining optimal water parameters
Velvet diseaseFine gold or yellow dust on the body, lethargy, loss of appetite, increased gill movementParasite (Oodinium pilularis)Use copper-based medicationMaintain high water quality, quarantine new fish


How Long Does Sundadanio Axelrodi Live?

Sundadanio Axelrodi lives about 3 to 5 years when they are kept in an aquarium environment that is well-maintained. 

However, factors such as their diet, the quality of water in their tank, and overall care can have a significant influence on their lifespan.

What Is the Ideal Tank Size for Sundadanio Axelrodi?

The ideal tank size for Sundadanio Axelrodi is a 10-gallon tank, but a 20-gallon tank or larger is recommended for their well-being.

Is Sundadanio Axelrodi Compatible with Other Fish?

Sundadanio Axelrodi is compatible with other fish and can coexist with many other species in a community tank. 

However, it’s important to avoid housing them with larger or aggressive species that might perceive them as food.

What Do Sundadanio Axelrodi Eat?

Sundadanio Axelrodi eats a diet that includes a variety of small insects, larvae, and crustaceans in their natural habitat. 

When kept in captivity, they should be provided with a varied diet of high-quality flake food or micro pellets, supplemented with live or frozen foods such as daphnia, brine shrimp, and bloodworms.


As promised, we’ve covered every detail necessary for providing the best care possible for your Sundadanio Axelrodi. 

From understanding their historical origins and natural behaviors, through to mastering the specifics of their diet, habitat requirements, and even breeding. 

Just remember, creating an environment that closely mimics their natural habitat and meeting their dietary needs are key to ensuring the health and longevity of your Sundadanio Axelrodi. 

Do you still have questions? If so, leave a comment and I’ll be happy to answer them.

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