Photo: Ltshears (CC BY-SA 3.0) — via Wikimedia Commons
Green Severum (Heros efasciatus)
A large, oval South American cichlid with gentle manners for its size — one of the few big cichlids that can genuinely share a tank.
Will it live with a Green Severum?
We compare each fish against your green severum on temperament, size, water parameters and swimming zone. Set your tank size and filter the results.
- Banjo Catfish✅ CompatiblePeaceful · 15 cm · Medium care · 20–26 °C (68–79 °F)
- Semi-aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Bearded Corydoras✅ CompatiblePeaceful · 10 cm · Medium care · 18–24 °C (64–75 °F)
- Semi-aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bearded Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Bristlenose Pleco✅ CompatiblePeaceful · 12 cm · Easy care · 23–30 °C (73–86 °F)
- Compatible on the things that matter: shared water near 23–29 °C, workable temperaments, and no predator-and-prey size gap.
- Clown Pleco✅ CompatiblePeaceful · 9 cm · Medium care · 24–28 °C (75–82 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Giant Kuhli Loach✅ CompatiblePeaceful · 12 cm · Easy care · 24–30 °C (75–86 °F)
- Semi-aggressive + Peaceful, but with no direct clash here, and their water overlaps around 24–29 °C — no size, zone or temperament conflicts.
- Leopard Frog Pleco✅ CompatiblePeaceful · 9 cm · Medium care · 25–30 °C (77–86 °F)
- Compatible on the things that matter: shared water near 25–29 °C, workable temperaments, and no predator-and-prey size gap.
- Marbled Hoplo✅ CompatiblePeaceful · 14 cm · Easy care · 22–28 °C (72–82 °F)
- Semi-aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–28 °C — no size, zone or temperament conflicts.
- Medusa Pleco✅ CompatiblePeaceful · 12 cm · Medium care · 26–30 °C (79–86 °F)
- Compatible on the things that matter: shared water near 26–29 °C, workable temperaments, and no predator-and-prey size gap.
- Porthole Catfish✅ CompatiblePeaceful · 10 cm · Easy care · 22–28 °C (72–82 °F)
- Semi-aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–28 °C — no size, zone or temperament conflicts.
- Rubber Lip Pleco✅ CompatiblePeaceful · 12 cm · Easy care · 20–26 °C (68–79 °F)
- Semi-aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–26 °C — no size, zone or temperament conflicts.
- Snowball Pleco✅ CompatiblePeaceful · 16 cm · Medium care · 24–30 °C (75–86 °F)
- Semi-aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Spotted Rubbernose Pleco✅ CompatiblePeaceful · 12 cm · Medium care · 20–26 °C (68–79 °F)
- Semi-aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Spotted Talking Catfish✅ CompatiblePeaceful · 15 cm · Easy care · 22–26 °C (72–79 °F)
- Semi-aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–26 °C — no size, zone or temperament conflicts.
- Striped Eel Loach✅ CompatiblePeaceful · 12 cm · Medium care · 24–28 °C (75–82 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Upside-down Catfish✅ CompatiblePeaceful · 10 cm · Easy care · 22–26 °C (72–79 °F)
- Compatible on the things that matter: shared water near 23–26 °C, workable temperaments, and no predator-and-prey size gap.
- Weather Loach✅ CompatiblePeaceful · 25 cm · Easy care · 5–24 °C (41–75 °F)
- Semi-aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Zebra Pleco✅ CompatiblePeaceful · 10 cm · Hard care · 26–30 °C (79–86 °F)
- Semi-aggressive + Peaceful, but with no direct clash here, and their water overlaps around 26–29 °C — no size, zone or temperament conflicts.
- Altifrons Geophagus⚠️ With cautionSemi-aggressive · 25 cm · Medium care · 24–28 °C (75–82 °F)
- Green Severum and Altifrons Geophagus can both be territorial; doable with space and dense planting, but watch for chasing.
- Your 208 L tank is below the ~378 L this pairing really wants — crowding raises aggression.
- Keep Altifrons Geophagus in a shoal of 6+ or it gets stressed and nippy.
- Angelicus Synodontis⚠️ With cautionSemi-aggressive · 25 cm · Medium care · 23–27 °C (73–81 °F)
- Green Severum and Angelicus Synodontis can both be territorial; doable with space and dense planting, but watch for chasing.
- Blood Parrot Cichlid⚠️ With cautionSemi-aggressive · 20 cm · Medium care · 24–28 °C (75–82 °F)
- Green Severum and Blood Parrot Cichlid can both be territorial; doable with space and dense planting, but watch for chasing.
- Discus⚠️ With cautionPeaceful · 20 cm · Hard care · 28–31 °C (82–88 °F)
- Green Severum and Discus are close in size, but the semi-aggressive one tends to dominate — add discus in a group to spread the pressure.
- Keep Discus in a shoal of 6+ or it gets stressed and nippy.
- Electric Blue Acara⚠️ With cautionSemi-aggressive · 16 cm · Medium care · 22–28 °C (72–82 °F)
- Both are a bit pushy (semi-aggressive + semi-aggressive) — workable only in a larger tank with cover and broken sight lines.
- Electric Blue Hap⚠️ With cautionSemi-aggressive · 20 cm · Medium care · 24–28 °C (75–82 °F)
- pH preferences only just meet (Green Severum 5.5–7.5 vs Electric Blue Hap 7.8–8.5) — target the overlap and acclimate slowly.
- Green Severum and Electric Blue Hap can both be territorial; doable with space and dense planting, but watch for chasing.
- Your 208 L tank is below the ~250 L this pairing really wants — crowding raises aggression.
- Emperor Peacock Cichlid⚠️ With cautionSemi-aggressive · 16 cm · Medium care · 24–28 °C (75–82 °F)
- pH preferences only just meet (Green Severum 5.5–7.5 vs Emperor Peacock Cichlid 7.6–8.6) — target the overlap and acclimate slowly.
- Green Severum and Emperor Peacock Cichlid can both be territorial; doable with space and dense planting, but watch for chasing.
- Your 208 L tank is below the ~210 L this pairing really wants — crowding raises aggression.
- Fire Blue Empress Cichlid⚠️ With cautionSemi-aggressive · 18 cm · Medium care · 24–28 °C (75–82 °F)
- Green Severum and Fire Blue Empress Cichlid can both be territorial; doable with space and dense planting, but watch for chasing.
- Your 208 L tank is below the ~400 L this pairing really wants — crowding raises aggression.
- Galaxy Pleco⚠️ With cautionSemi-aggressive · 25 cm · Medium care · 22–26 °C (72–79 °F)
- Green Severum and Galaxy Pleco can both be territorial; doable with space and dense planting, but watch for chasing.
- Goldie Pleco⚠️ With cautionSemi-aggressive · 20 cm · Medium care · 24–29 °C (75–84 °F)
- Green Severum and Goldie Pleco can both be territorial; doable with space and dense planting, but watch for chasing.
- Guyana Flag Cichlid⚠️ With cautionSemi-aggressive · 18 cm · Medium care · 24–30 °C (75–86 °F)
- Both are a bit pushy (semi-aggressive + semi-aggressive) — workable only in a larger tank with cover and broken sight lines.
- Honeycomb Pleco⚠️ With cautionSemi-aggressive · 21 cm · Medium care · 24–29 °C (75–84 °F)
- Green Severum and Honeycomb Pleco can both be territorial; doable with space and dense planting, but watch for chasing.
- Your 208 L tank is below the ~280 L this pairing really wants — crowding raises aggression.
- Platinum Acara⚠️ With cautionSemi-aggressive · 20 cm · Medium care · 23–28 °C (73–82 °F)
- Both are a bit pushy (semi-aggressive + semi-aggressive) — workable only in a larger tank with cover and broken sight lines.
- Spanner Barb⚠️ With cautionSemi-aggressive · 18 cm · Medium care · 23–29 °C (73–84 °F)
- Both are a bit pushy (semi-aggressive + semi-aggressive) — workable only in a larger tank with cover and broken sight lines.
- Spanner Barb is a notorious fin-nipper — even though Green Severum is larger, an active shoal will harass its trailing fins. Only safe in a full group of 6+ with plenty of cover.
- Keep Spanner Barb in a shoal of 6+ or it gets stressed and nippy.
- Striped Raphael Catfish⚠️ With cautionSemi-aggressive · 20 cm · Medium care · 24–28 °C (75–82 °F)
- Green Severum and Striped Raphael Catfish can both be territorial; doable with space and dense planting, but watch for chasing.
- Tiger Loach⚠️ With cautionSemi-aggressive · 20 cm · Medium care · 23–27 °C (73–81 °F)
- Both are a bit pushy (semi-aggressive + semi-aggressive) — workable only in a larger tank with cover and broken sight lines.
- Alligator Gar⛔ Not recommendedAggressive · 250 cm · Hard care · 24–28 °C (75–82 °F)
- Two assertive fish, one genuinely aggressive: Green Severum and Alligator Gar will hold territory and clash.
- Alligator Gar (250 cm) is big enough to swallow the 20 cm Green Severum whole.
- Your 208 L tank is below the ~3785 L this pairing really wants — crowding raises aggression.
- Clown Knifefish⛔ Not recommendedAggressive · 90 cm · Hard care · 24–28 °C (75–82 °F)
- Green Severum and Clown Knifefish are both territorial and at least one is outright aggressive — expect serious fighting.
- Size gap is too large (90 vs 20 cm): Clown Knifefish will treat Green Severum as food.
- Your 208 L tank is below the ~750 L this pairing really wants — crowding raises aggression.
- Fire Eel⛔ Not recommendedSemi-aggressive · 100 cm · Medium care · 24–28 °C (75–82 °F)
- Fire Eel (100 cm) is big enough to swallow the 20 cm Green Severum whole.
- Both are a bit pushy (semi-aggressive + semi-aggressive) — workable only in a larger tank with cover and broken sight lines.
- Your 208 L tank is below the ~380 L this pairing really wants — crowding raises aggression.
- Koi⛔ Not recommendedPeaceful · 90 cm · Medium care · 4–28 °C (39–82 °F)
- Size gap is too large (90 vs 20 cm): Koi will treat Green Severum as food.
- Your 208 L tank is below the ~3800 L this pairing really wants — crowding raises aggression.
- Redtail Catfish⛔ Not recommendedAggressive · 120 cm · Hard care · 24–27 °C (75–81 °F)
- Two assertive fish, one genuinely aggressive: Green Severum and Redtail Catfish will hold territory and clash.
- Size gap is too large (120 vs 20 cm): Redtail Catfish will treat Green Severum as food.
- Your 208 L tank is below the ~5700 L this pairing really wants — crowding raises aggression.
- Spotted Gar⛔ Not recommendedAggressive · 90 cm · Hard care · 18–26 °C (64–79 °F)
- Two assertive fish, one genuinely aggressive: Green Severum and Spotted Gar will hold territory and clash.
- Size gap is too large (90 vs 20 cm): Spotted Gar will treat Green Severum as food.
- Your 208 L tank is below the ~600 L this pairing really wants — crowding raises aggression.
- Wels Catfish⛔ Not recommendedAggressive · 300 cm · Hard care · 15–25 °C (59–77 °F)
- Two assertive fish, one genuinely aggressive: Green Severum and Wels Catfish will hold territory and clash.
- Size gap is too large (300 vs 20 cm): Wels Catfish will treat Green Severum as food.
- Your 208 L tank is below the ~20000 L this pairing really wants — crowding raises aggression.
- Wolf Cichlid⛔ Not recommendedAggressive · 72 cm · Hard care · 24–30 °C (75–86 °F)
- Green Severum and Wolf Cichlid are both territorial and at least one is outright aggressive — expect serious fighting.
- Green Severum is bite-sized to a 72 cm predatory wolf cichlid — it will be eaten.
- Your 208 L tank is below the ~760 L this pairing really wants — crowding raises aggression.
Compatibility is computed from each species' care data — a strong starting point, not a guarantee. Individual temperament varies, so always introduce new fish slowly and watch them.
Green Severum care specs
- Care level
- Medium
- Breeding
- Medium
- Max size
- 20 cm (7.9 in)
- Min tank size
- 208 L (55 gal)
- Temperature
- 23–29 °C (73–84 °F)
- pH
- 5.5–7.5
- Hardness
- 1–10 dGH
- Lifespan
- 8–12 years
- Diet
- Omnivore
- Swim level
- Middle
- Group size
- Best alone or in a pair
- Family
- Cichlidae
- Origin
- South America — Amazon and Orinoco river basins (Brazil, Colombia, Venezuela)
What is a Green Severum?
The Green Severum (Heros efasciatus) is a deep-bodied, disc-shaped cichlid native to the Amazon and Orinoco river basins of South America. It grows to around 20 cm (8 in) in the aquarium — large by community-tank standards — and carries the laterally compressed, high-backed oval silhouette that draws inevitable comparisons to discus. Wild specimens are olive-green with five to eight dark vertical bars, the hindmost being the most sharply defined. Decades of captive breeding have also produced gold and turquoise colour morphs that are now just as commonly offered in the trade as the original green form.
What sets the Green Severum apart from most large cichlids is personality. It earns its nickname “the gentleman’s cichlid” through genuine tolerance toward appropriately sized companions — a rarity at this body size. That said, the temperament is semi-aggressive, not peaceful: it will defend territory during spawning and will readily eat anything small enough to fit in its mouth. Understanding where that line falls is the foundation of keeping severums successfully in a community setting.
Where do Green Severums come from?
Heros efasciatus is native to the slow-moving and seasonally flooded reaches of the Amazon basin in Brazil and the Orinoco drainage extending into Colombia and Venezuela — the same vast soft-water geography that also gave us discus, angelfish and geophagus. In the wild, severums inhabit blackwater and clearwater rivers, flooded forest (igapó and várzea), oxbow lakes and marginal lagoons where the water is warm, soft and mildly to moderately acidic. Submerged wood, trailing roots and dense leaf litter provide shelter and foraging ground.
Virtually all fish in today’s trade are captive-bred, which makes them more adaptable to near-neutral pH than their wild ancestors. Their preference for soft, slightly acidic water is nonetheless real and worth respecting for long-term health, colouration and willingness to breed.
What size tank does a Green Severum need?
The minimum for a single adult is 208 litres (55 gal), and that is genuinely the floor. A pair or a mixed community needs at least 300–380 L (80–100 gal), with a footprint that prioritises length over height — severums are active mid-water swimmers that cruise long, unhurried circuits and need the room to do so comfortably.
Aquascape with large pieces of driftwood and smooth flat stones to create visual breaks and potential spawning surfaces. Planting is welcome, but choose robust, fast-growing species — vallisneria, Amazon swords and hornwort — because severums dig enthusiastically during breeding and will uproot anything delicate. Substrate can be coarse sand or fine gravel; sand is ideal if you plan to breed them, as the pair will excavate a pit ahead of spawning. Keep lighting moderate and provide shaded areas using wood overhangs or broad-leafed plants; in bright, exposed tanks severums can be shy and show washed-out colour.
What water parameters do Green Severums need?
- Temperature: 23–29 °C (73–84 °F). The species tolerates a wide band, but aim for the 25–27 °C (77–81 °F) sweet spot for day-to-day keeping.
- pH: 5.5–7.5. Captive-bred fish handle neutral water well; wild-caught or breeding fish benefit from slightly acidic conditions.
- Hardness: 1–10 dGH. Soft water is preferred and is important for spawning success.
Excellent water quality is non-negotiable for a fish with a lifespan of 8–12 years that produces significant waste. Run a robust biological filter — canister filters are a natural fit for a large, planted cichlid tank — and perform 25–30% weekly water changes. A cycled tank, stable parameters and consistent maintenance are far more important than chasing a precise pH number. Avoid sudden swings: the species is sensitive to parameter instability even though it can adapt to a wide range over time.
What do Green Severums eat?
Green Severums are omnivores with a bias toward plant and algal matter in the wild, where they graze on aufwuchs, soft vegetation and fallen fruit alongside invertebrates. In the aquarium, a varied, plant-leaning diet keeps colour vivid and digestion healthy:
- Staple: High-quality cichlid pellets or granules sized appropriately for a 20 cm (8 in) fish.
- Vegetables: Blanched spinach, zucchini, peas and spirulina-enriched foods are eagerly accepted and important for gut health.
- Protein: Frozen bloodworms, earthworms, krill and occasional live foods round out the diet. Feed protein items two or three times per week rather than as a daily staple.
Feed once or twice daily in amounts the fish clears in two to three minutes. Severums are not gluttonous by cichlid standards, but overfeeding still degrades water quality fast in a tank of this bioload. Remove uneaten food promptly.
Are Green Severums aggressive — and what fish can live with them?
The Green Severum is rated semi-aggressive: calm enough outside of breeding to coexist with a carefully chosen community, but assertive enough to bully smaller or weaker fish and to eat anything bite-sized. The aggression dial turns up noticeably during courtship and spawning, when even established companions may need to be removed temporarily if a pair becomes very protective of their site.
Ideal tank-mates share the species’ soft, warm-water requirements and are large enough not to be intimidated or consumed:
- Other severums (keeping a compatible pair or a group of juveniles raised together)
- Eartheaters (Geophagus spp.) — similar temperament and water needs
- Larger schooling tetras such as Buenos Aires tetras or Congo tetras
- Robust plecos (common pleco, bristlenose) and armoured catfish like the striped raphael
- Oscars and other large South American cichlids can work in very large tanks but require careful monitoring
Avoid small tetras, livebearers, dwarf cichlids, shrimp and any fish under roughly 5–6 cm that will be treated as prey. Avoid known fin-nippers such as tiger barbs, which will harass the severum’s softer fins.
For a curated, filterable list of compatible and incompatible species, see Green Severum tank mates.
How do you tell male from female Green Severums?
Juvenile severums are notoriously difficult to sex, and many keepers buy a group of youngsters and allow natural pairs to form. As the fish mature, the differences become clear:
Males develop distinctive orange-red facial markings — worm-like lines and spots on the cheeks, forehead and chin — and show brighter, more saturated colouration on the throat and lower fins. The dorsal fin often extends into a longer, more pointed tip in males.
Females remain plainer overall: the face stays olive-green to yellowish without the red facial patterning, the body colouration is softer, and females tend to be slightly smaller and noticeably rounder through the belly when gravid and approaching spawning condition.
How do Green Severums breed?
Breeding is achievable in the home aquarium and is rated medium difficulty. A compatible pair will typically form naturally if you raise several juveniles together and remove rivals once a bond establishes. The pair should be conditioned on a varied, protein-enriched diet before spawning.
Spawning behaviour follows the classic open-substrate cichlid pattern. The pair cleans a flat stone or the tank floor vigorously before the female deposits a clutch of eggs (often several hundred), which the male then fertilises. Both parents share guarding duties actively, fanning the eggs and chasing away any perceived threats — including their former tank-mates. Water temperature at the upper end of the range (27–29 °C / 81–84 °F) and slightly softened, acidic water encourages spawning.
Eggs hatch in approximately 48–72 hours depending on temperature; the fry become free-swimming after another four to five days. Both parents continue guarding the fry for several weeks. First foods for fry include freshly hatched brine shrimp nauplii and fine powdered fry food. Having a dedicated breeding tank or a separate rearing vessel for the fry improves survival rates significantly.
What diseases commonly affect Green Severums?
Green Severums are hardy fish when water quality is maintained, but they are susceptible to the standard freshwater cichlid ailments:
- Hole-in-the-Head (HITH) / Head and Lateral Line Erosion (HLLE): Pitting around the lateral line and head — strongly associated with poor water quality, activated carbon overuse and dietary deficiencies (particularly vitamin C and D). Prevention is the best cure: keep water pristine, feed a varied diet and avoid long-term carbon use.
- Ich (white-spot disease): Small white pinhead spots across the body; almost always triggered by stress or a sudden temperature drop. Raising temperature slightly and maintaining good conditions is the first line of defence.
- Internal parasites: Wild-caught fish in particular may arrive with intestinal worms; watch for hollow belly despite a good appetite and stringy, pale faeces.
- Fin rot: Ragged or receding fin edges, almost always a water-quality problem. Improve conditions before any other intervention.
Health note: this profile covers prevention and husbandry. For sick fish, confirm symptoms against a reputable veterinary or aquatic-health source before beginning any treatment.
How long do Green Severums live?
A well-kept Green Severum lives 8–12 years — a substantial commitment that prospective owners should weigh carefully before purchase. Fish maintained in correct water conditions, fed a varied diet and housed in appropriately sized quarters consistently reach the top of that range. The lifespan is one of the species’ most appealing traits: a bonded pair that settles and breeds in a mature display tank can be a centrepiece for the better part of a decade. Give them space, clean water and attentive husbandry and the Green Severum will reward you with one of the more rewarding long-term relationships available in the freshwater hobby.
Frequently asked questions
Can Green Severums live with other fish?
Yes, with careful selection. They are unusually tolerant for a cichlid of their size, but will bully and eat anything small enough to swallow. Good tank-mates are similarly sized fish that prefer soft, warm water — larger tetras, eartheaters, severums of the same species, and robust catfish such as plecos or striped raphael catfish.
How do you tell male and female Green Severums apart?
Adult males develop distinctive orange-red facial markings and often show bright coloration on the throat and lower fins; females remain more subdued in colour and are slightly smaller and rounder-bodied when ready to spawn.
What you need to keep a green severum
The baseline is a heated, filtered 208 L+ tank: a reliable heater to hold 23–29 °C (73–84 °F), a gentle filter that won't batter a green severum in the current, and a tight-fitting lid. Cycle the tank fully before adding any fish.
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