Red Phantom Tetra
Hyphessobrycon sweglesi
A deep-red, disc-shaped gem with a prominent 'phantom' black spot. Highly schooling, but has a strict requirement: it needs unusually cool water (20-23°C) and will waste away if kept too hot.
Water Temperature
20 - 25 °C
pH Value
6 - 7.5
Water type
Freshwater
Tank level
Middle
Adult size
4.5 cm
Minimum tank volume
>= 60 L
Minimum group
>= 6
GH
2 - 15 dGH
KH
1 - 7 dKH
TDS
40 - 295 ppm
Conductivity
63 - 461 uS/cm
Species description
Geographical Origin and Habitat: Endemic to the upper Orinoco River basin in Colombia. Inhabits clear, highly oxygenated, and relatively cool, shaded forest streams with moderate flow.
Taxonomy and Morphology: Hyphessobrycon genus (deep-bodied tetras). Reaches about 4 cm. Round, disk-like shape rather than a torpedo profile. Males possess a dramatically elongated dorsal fin resembling a ship's sail.
Social Behavior: Peaceful and strictly schooling. They occupy the middle/bottom of the tank in a tight group. Males perform stunning mock-battles, erecting their massive dorsal fins and circling each other to establish dominance, a completely harmless but beautiful display.
Coloration and Sexual Dimorphism: Semi-transparent body heavily washed in bright carmine/blood red. A distinctive, large round black spot sits squarely on the flank behind the gills. Males are intensely red with a towering, pointed dorsal fin. Females are plumper with a short, rounded dorsal fin tipped prominently in white.
Care, breeding and tankmates
Aquarium Setup: Minimum 60-80 cm (24-30 inches). Demands a dark substrate and dense edge planting to feel secure. If kept in brightly lit, bare tanks over white gravel, their red completely washes out to a stressed, transparent pink. Floating plants are recommended to dim the light.
Diet and Feeding: Micro-omnivore. Happily takes high-quality color-enhancing micro-pellets (astaxanthin helps the red). Must be fed frozen daphnia or brine shrimp weekly to maintain optimal health and coloration.
Water Quality: THE CRITICAL FACTOR IS TEMPERATURE: This is a cool-water tropical fish. Ideal temps are 20-23°C (68-73°F). If kept at standard tropical temps (26°C+ / 79°F+), their metabolism burns out, they lose color, and quickly die from bacterial infections. Demands soft, slightly acidic water (pH 5.0-6.5) with high oxygenation.
Compatibility and Cohabitation: Do NOT keep with Discus, German Blue Rams, or Cardinal Tetras (the temperature needs are completely incompatible). Perfect tankmates are cool-water Corydoras (Panda, Paleatus) or Hillstream Loaches. Must be kept in schools of 8-10+; kept in small numbers, they will hide constantly.
Aquarium Breeding: Challenging. Requires a dedicated, pitch-black spawning tank with peat moss. Parents eat the eggs instantly if not removed. Eggs are highly photosensitive and will fungus if exposed to bright light.
Risks and Diseases: 1. Rapid death and wasting due to being kept in warm 'standard' tropical tanks (26°C+). 2. Complete color loss from stress, bright lights, or small school sizes.
Geographic Origin and Distribution
Endemic to the upper Orinoco River basin in Colombia. Inhabits clear, highly oxygenated, and relatively cool, shaded forest streams with moderate flow.
Origin
Tropical oceans and reefsAmazon, Orinoco, and Guianas
Fish profile
- Temperament
- Semi-aggressive
- The Hyphessobrycon sweglesi is renowned for its peaceful, albeit somewhat shy and timid, temperament. They are highly social fish that absolutely depend on the presence of a sizable school for their confidence and well-being. When kept in sufficient numbers, they exhibit a lively and inquisitive nature, gracefully exploring the aquarium. However, if kept alone or in very small groups, they will likely become withdrawn, pale, and prone to hiding constantly.
- Diet
- Omnivore
- In its natural habitat, the Hyphessobrycon sweglesi is a micro-predator that primarily feeds on tiny invertebrates and zooplankton. In captivity, they eagerly accept a staple diet of high-quality crushed flakes and micro-pellets. To support their overall health and promote optimal development—such as their stunning translucent red body with a dark shoulder patch—their diet should be frequently supplemented with live or frozen foods like Daphnia and cyclops. A diverse nutritional profile is crucial for maintaining a robust immune system.
- Life expectancy
- 3-5 years
- The life expectancy of Hyphessobrycon sweglesi in captivity is generally between 3 and 5 years when kept under optimal environmental conditions. To maximize their longevity, it is essential to ensure water temperatures that are unusually cool for an Amazonian fish, preferably between 20°C and 23°C (68°F and 73°F). Constantly high temperatures accelerate their metabolism, significantly shortening their lifespan and making them more vulnerable to disease.
- Adult size
- 4.5 cm
- The catalog's scalar value is 4.5 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 3.2 cm for this species, recorded as standard length (SL). The taxonomic link follows a synonym to the FishBase SPECIES table (v25.04 snapshot) record for Megalamphodus sweglesi (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- School
- When establishing a school of Hyphessobrycon sweglesi, maintaining a relatively balanced mix of males and females is beneficial. Males generally exhibit a slimmer profile and often display their characteristic vibrant red coloration more intensely compared to the plumper females. Having slightly more females than males can help dissipate any minor intra-species sparring when males display for dominance. Ultimately, keeping a large enough overall group size is more critical than the exact sex ratio.
- Feeding frequency
- Twice daily
- For optimal health, the Hyphessobrycon sweglesi should be fed small portions two to three times a day. Only offer an amount of food that the school can completely consume within two minutes to prevent water fouling. Overfeeding is a common issue with small characins, so strict portion control must be maintained. This frequent, small-meal approach closely mimics their continuous foraging behavior in the wild.
- Bioload
- The Hyphessobrycon sweglesi contributes a very low bioload to the aquarium ecosystem due to its small size. This makes them highly suitable for densely planted nano tanks and community setups alike. Despite their low waste production, maintaining a strict schedule of weekly water changes is highly recommended. A standard, high-quality biological filtration system will easily process the minimal waste generated by a healthy school.
- Flow
- Stagnant
- The Hyphessobrycon sweglesi naturally inhabits slow-moving streams and flooded forest areas, meaning they prefer gentle water flow in the aquarium. Strong currents from overpowered filters can quickly exhaust these small fish and cause chronic stress. A sponge filter or a baffled hang-on-back filter is usually the most appropriate choice to provide oxygenation without turbulent flow. Providing dense clusters of aquatic plants will also give them tranquil resting spots.
- Reproduction
- Oviparous
- Breeding the Hyphessobrycon sweglesi requires a separate, dimly lit breeding tank equipped with soft, slightly acidic water. They are typical egg-scatterers that exhibit no parental care whatsoever, and they will readily consume their own eggs if left in the breeding tank. Spawning typically occurs among fine-leaved plants, after which the adults must be immediately removed. The microscopic fry require infusoria or specialized liquid foods until they are large enough to eat freshly hatched brine shrimp.
- Compatibility & tankmates
- As a peaceful schooling species, the Hyphessobrycon sweglesi thrives when kept in a vibrant community aquarium. They require the security of a group, so maintaining them in schools of at least eight individuals is essential. Excellent tank mates include small rasboras, Corydoras catfish, and other equally peaceful characins. Aggressive, large, or excessively boisterous fish should be strictly avoided to prevent them from becoming stressed or preyed upon.
- Tank level
- Middle
- The Hyphessobrycon sweglesi is an active swimmer that primarily occupies the mid to upper levels of the aquarium water column. They deeply appreciate having a large, open swimming space in the center of the tank to school properly. They will often dart around the middle strata during the day, occasionally diving to the substrate during feeding times. Tall background plants and floating vegetation help them feel secure in these preferred swimming zones.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.2 ± 0.37 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.5002
- Bayesian Length-Weight
- a = 0.01995, b = 3.01
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
