One-Spotted Demonfish
Satanoperca lilith
The 'One-Spotted Demon Eartheater' (25 cm). The genus Satanoperca (Demonfish) includes the most pointed and bizarre-snouted sand sifters of South America. The Satanoperca lilith is an extraordinary rarity, distinguishable from congeners by the conspicuous single dark spot on the upper flank and by the marked juvenile vertical bands. Inhabitant of the extreme Amazonian blackwaters (Rio Negro), it is a very shy, strictly peaceful and schooling fish, which demands an environment of purest blackwater, impalpable sand and a darkened, tranquil environment so as not to let itself die of stress and starvation.
Water Temperature
27 - 31 °C
pH Value
4.5 - 6
Water type
Freshwater
Tank level
Bottom
Adult size
25 cm
Minimum tank volume
>= 300 L
Minimum group
6 - 8
GH
1 - 4 dGH
KH
1 - 2 dKH
TDS
25 - 80 ppm
Conductivity
39 - 125 uS/cm
Species description
Geographical Origin and Habitat: The Spirit of the Black Waters. Populates the slow-flowing stretches, oxbow lakes and flooded forests of the Rio Negro and Rio Branco basins in Brazil. The habitat is extreme: white quartz sand bottoms buried under a meter of rubber tree (Hevea) leaves, intricate sunken branches and very dark coffee-colored water, hot as a thermal bath and devoid of any calcareous mineral.
Taxonomy and Morphology: The Anteater Profile. The name *Satanoperca* (demon perch) contrasts with its mild nature, perhaps deriving from the sharp profiles of the snout reminiscent of grotesque masks. The head of the *lilith* is very long, with a straight and sloping forehead and a tubular mouth placed on the bottom. High and compressed body (reaches 25-26 cm / 10 inches). The eyes are large and positioned very high on the skull to monitor the environment while the mouth is immersed in the sand.
Social Behavior: The Shy Gregarious of the Shadows. Neurotically peaceful and fragile fish. Lives in schools (absolutely mandatory a group of 6-8 specimens) and spends its days vacuuming sand. Extremely susceptible to stress: abrupt external movements, strong lights or turbulent tankmates condemn it to a rapid and lethal feeding block. It must be flanked only by equally peaceful and pelagic fish ("dither fish") to instill security.
Coloration and Sexual Dimorphism: Sapphire Camouflage and the Unique Mark. The base color is a pale Silver/Olive Grey designed to disappear in the dark. THE DIAGNOSTIC TRAIT: unlike the famous *S. daemon* which possesses 2-3 spots, the *lilith* possesses ONLY ONE large black spot on the upper back (under the dorsal fin), plus a small ocellus on the caudal peduncle. Cheeks and snout are studded with metallic neon blue luminescence. Sexes are monomorphic (identical to the naked eye).
Care, breeding and tankmates
Aquarium Setup: Demands "Shadow and White Sand" (Tank min. 160-200 cm / 6-7 ft). THE ABSOLUTE DOGMA IS FINE SAND AND DARKNESS. Gravel or crushed stone destroy the gills and cause death by asphyxiation and bacterial mouth infections. Insert thick layers of white sand (5-10 cm / 2-4 in), a graveyard of large dry leaves (Catappa, Oak) and intricate branches. Very dim light, almost dark, shielded by a mantle of very thick floating plants.
Diet and Feeding: Benthic Omnivorous Siphon. Initially critical feeding (they refuse tablet feeds when newly introduced). Demands food that rains to the bottom to vacuum it from the sand: frozen brine shrimp, red bloodworms, daphnia, well-cleaned live tubifex. After acclimatization (weeks), it will accept slow sinking small-sized carnivorous pellets. Gasping at the surface kills or bloats it.
Water Quality: Thermal Blackwater Necessity. The animal succumbs in bare city tap-water tanks. DEMANDS hot kettle water (27-31°C / 81-88°F; at 24°C / 75°F it stops eating and wastes away in 10 days). Chemically the water MUST be peaty, extremely soft (GH 1-4) and acidic (pH 4.5 - 6.0). Nitrates tolerated close to zero: mandatory titanic and slow partial water changes.
Compatibility and Cohabitation: Community of Fear (Dither Fish Tank). The aquarium must reassure the demon. Vital companions: gigantic schools of very calm small/medium pelagic characins (Neon Tetras, Cardinals, Nannostomus) which, swimming serenely at the surface, indicate to the *lilith* the absence of feathered predators. Absolutely exclude cichlasomines, pikes or enormous territorial loricariids.
Aquarium Breeding: Mysterious Mouthbrooders. Extremely rare in captivity. They lay hidden eggs under leaves or in wood cavities. Despite few precise records, like many of the *daemon* group, parents protect the brood fiercely defending the perimeter, and mouthbrood or very closely guard the nest of larvae (pit nests).
Risks and Diseases: Neotropical Bloat Lethality (HITH/Flagellates). The most susceptible fish in the world to intestinal flagellates due to environmental stress (Satanoperca Bloat/Hole in the Head). Lack of sand, cold thermal swings, non-acidic water or pesky tankmates trigger enormous purulent cranial ulcers and irreversible knife-blade anorexic weight loss.
Geographic origin and distribution
The Spirit of the Black Waters. Populates the slow-flowing stretches, oxbow lakes and flooded forests of the Rio Negro and Rio Branco basins in Brazil. The habitat is extreme: white quartz sand bottoms buried under a meter of rubber tree (Hevea) leaves, intricate sunken branches and very dark coffee-colored water, hot as a thermal bath and devoid of any calcareous mineral.
Origin
Tropical oceans and reefsAmazon, Orinoco, and GuianasEurope, Mediterranean, and West Asia
Fish profile
- Temperament
- Semi-aggressive
- They are gentle giants with a peaceful disposition. They are fascinating to watch as they socially interact within their group. They do not tolerate aggressive tankmates well.
- Diet
- Omnivore
- They are specialized earth-eaters requiring a sandy substrate. They eagerly accept high-quality sinking pellets and frozen bloodworms. Ensure the food reaches the bottom quickly.
- Life expectancy
- 6-10 years
- Adult size
- 25 cm
- Sex ratio
- Solitary
- They should be kept in a group of at least 5 individuals. Intraspecific aggression is minimal when kept in proper numbers. Single individuals will become withdrawn and stressed.
- Feeding frequency
- Twice daily
- Feed them twice a day with moderate portions. They spend all day foraging, so spreading out meals is beneficial. Avoid overfeeding to prevent digestive blockages.
- Bioload
- High
- This large species contributes a heavy bioload. Strong biological and mechanical filtration are absolutely essential. Water quality must be impeccable, requiring large, regular water changes.
- Flow
- Stagnant
- Moderate water flow is best for this species. They prefer calm areas near the bottom to sift in peace. Ensure good surface agitation for oxygenation.
- Jump risk
- No
- Reproduction
- Oviparous
- Breeding is exceptionally rare in captivity. They are believed to be delayed mouthbrooders. Simulating the wet season with soft, cool water changes may trigger spawning.
- Compatibility & tankmates
- Peaceful
- It is peaceful but grows quite large. It should be kept with other large, non-aggressive species like Geophagus or Severums. Small fish may be swallowed accidentally during feeding.
- Tank level
- Bottom
- They are almost entirely bottom-dwelling fish. They cruise just above the sandbed, constantly sifting. They require a very large footprint in the aquarium.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
FishBase v25.04Data synced on: 06/15/2026
- Trophic level
- 3.1 ± 0.4 se
- Resilience
- Medium (1.4 - 4.4 years)
- Phylogenetic uniqueness (PD50)
- 0.5039
- Bayesian Length-Weight
- a = 0.02399, b = 3.01
- VulnerabilityLow vulnerability (21 / 100)
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
