Green Severum Care Guide

The green severum is the "poor man's discus" - a big, deep-bodied, disc-shaped South American cichlid that is genuinely placid for its size and rarely injures tankmates in a squabble. But gentle is not the same as harmless. It reaches roughly 20 cm, eats any fish small enough to fit in its mouth, mows soft plants like a lawnmower and produces a heavy bioload. The trap is buying it as a calm "community" fish and then stocking it with small fish (snacks), live soft plants (salad) and too small a tank.

Green Severum at a glance

The sourced figures the welfare engine uses to judge Green Severum — the parseable key facts.

Where it comes from

Severums come from the Amazon basin - tributaries of the Ucayali and Solimoes-Amazon in Peru and Brazil, with records from the rio Negro and rio Xingu. They are benthopelagic fish of slow-moving rivers, tributaries and floodplain lakes, most abundant in deeper, calm water full of submerged tree roots and branches. That biotope shapes the care: they want a long, deep tank with driftwood, bogwood, caves and shade, ideally a tannin-stained black-water style, and gentle filtration rather than high current to match the calm floodplain origin. Their wild water is warm, soft and slightly acidic, which is preferred and closer to essential for spawning, though they tolerate harder water. And because they are frugivores of the flooded forest, feeding on fruit and seeds in the wet season, they come to the tank with a strong appetite for plant matter - which is exactly why they eat aquarium plants.

Did you know?

• It is one of the few cichlids that acts as a regular frugivore, feeding on fruits and seeds in the flooded Amazon forest during the wet season.
• Its tall, disc-shaped body and comparatively calm nature make it the classic "poor man's discus" - a hardy stand-in for the far fussier real thing.
• A 175-year mistake was fixed in 2015: the fish the hobby called "H. severus" for over a century turned out to be a different, mouthbrooding species (renamed H. liberifer) when the true, rare H. severus was rediscovered by its tell-tale partial seventh band.
• You can read a mature male's face: he "writes" worm-like squiggles across his cheeks and gill plates, a living sexing chart for the green form.
• Despite its size it is a devoted, role-sharing parent - a substrate-spawning pair cleans a stone, lays, and both guard the eggs and fry together.

Tank size — and why

Tank size here is about adult size and bioload, not territorial display. Seriously Fish considers a severum unsuitable for anything under a 120 cm (48-inch) tank of about 243 litres, roughly 64 US gallons, while AquariumStoreDepot gives 55 gallons for a single fish and 75-plus for a pair or community. Treat 55 gallons as a realistic floor for one adult and 75-plus as the right answer for a pair or any community. The fish swims the whole water column, grows fast - a four-inch severum becomes an eight-inch severum quicker than you expect - and is a heavy waste producer, so the space buys water volume and reduced aggression. A cramped severum becomes a stressed, aggressive severum.

As a guide, a 55-gallon tank comfortably suits about 1 Green Severum as a single-species display, leaving room for tankmates.

How big does it really get?

Full-grown Green Severum reach about 20 cm (7.9 in) long, but they are usually sold at only about 4 cm (1.6 in) — a typical shop size (estimate). At full size, Green Severum needs roughly a 55-gallon tank, about 122 cm long; a common 10-gallon starter kit is only about 51 cm.

Adult size is sourced; the shop size is a typical-juvenile estimate; tank length is approximate for a standard 55-gallon aquarium.

Water parameters in practice

Aim for about 25-29 C and a soft, slightly acidic pH around 6.0-7.0, with a tolerated band of roughly 22-32 C and pH 5.5-7.5; soft-to-moderate hardness (around 1-8 dH) matches the wild fish, though they cope with harder water. It is less fragile than discus or a ram - that is the whole basis of the "hardy alternative to discus" pitch - but the heavy bioload makes stable, clean water non-negotiable, and stability matters more than chasing an exact number. Soft, slightly acidic water is preferred generally and becomes close to essential if you want them to spawn.

Diet & feeding

In the wild the severum is an omnivore that is primarily frugivorous - one of the few cichlids that regularly eats fruit and seeds, alongside plant matter and small invertebrates. In the tank, lean the diet toward vegetables: a quality cichlid or spirulina pellet and flake base, plus blanched spinach, courgette, cucumber and peas, with only occasional bloodworm, brine shrimp or chopped earthworm and prawn. Avoid beef heart and liver - mammalian fat is poorly handled and a noted cause of bloat. Feed once or twice a day without overfeeding the heavy bioload. Two behaviours matter for stocking: it will eat any fish small enough to swallow, opportunistically rather than as a dedicated hunter, and it mows down soft plants, so a prized live-plant aquascape and a severum rarely coexist.

Gear & setup

Sand or fine gravel, driftwood and bogwood, river-rock caves and shade suit them best, with a tannin-stained black-water feel ideal. For planting, expect soft stem plants to be eaten or uprooted - use tough, unpalatable species such as java fern, anubias or Bolbitis, or go with hardscape and artificial plants. Strong filtration handles the high bioload, but keep the flow gentle to match the calm-water origin. Keep the tank covered, as with any large cichlid.

Temperament & behaviour

Seriously Fish calls the severum fairly mild-mannered for a cichlid of this size, and disputes rarely cause serious injury - but it is still a large, semi-aggressive cichlid, not a peaceful nano fish. A lone fish or an established pair is usually calm in a tank with adequate volume and sightline breaks; a cramped severum gets stressed and aggressive. It is not a hunter by temperament, but it is opportunistic and will take anything small enough to swallow. Toward its own kind it is mostly easygoing - which is why low intraspecific aggression gets repeated - though maturing and pairing fish can become territorial around a spawning site, so the calm baseline is real but breeding is the exception to watch.

Group & social needs

Severums are happy kept singly or as a bonded male-female pair. Many keepers grow out a group of four or more juveniles to let a pair form naturally and to spread out any aggression, since there is no reliable way to force-pair two adults. It is not a schooling fish, so a single specimen is perfectly content, and a settled pair is the usual route to breeding.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Green Severum and that suit its size and temperament best. Tap any to load the pairing in the planner.

• Boesemani Rainbowfish — Peaceful temperament, similar adult size.
• Bristlenose Pleco — Peaceful temperament, similar adult size.
• Keyhole Cichlid — Peaceful temperament, similar adult size.

This engine-cleared shortlist is Green Severum's tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Breeding is of moderate difficulty - a compatible pair spawns readily, and the real hurdle is getting a true pair, which is why growing out a group is the standard approach. Correct the usual error first: the green severum is Heros efasciatus, a substrate spawner with biparental care, not a mouthbrooder. The mouthbrooding fish long sold as "H. severus" was actually a separate species, renamed H. liberifer in 2015 when the true, rare H. severus was rediscovered - which is exactly why so many old guides wrongly describe "severums" as mouthbrooders. Sexing young fish is hard; mature males develop worm-like "vermiculation" squiggles across the face and gill covers (reportedly accurate around 90 percent of the time, though not failsafe and not on every colour form), plus a nuchal hump and extended, pointed fins, while females are rounder and plainer, often with a dark blotch in the dorsal. To trigger spawning, give soft, slightly acidic warm water (around 26-27 C), a flat spawning surface and good conditioning. Clutches are large - commonly several hundred eggs, with high-end hobby reports up to about a thousand, though a precise figure specific to H. efasciatus is poorly documented - and both parents clean a stone or pit, guard the eggs and shepherd the free-swimming fry. The gold (xanthic) strain is widely said to be harder to breed, but that is hobby anecdote rather than established fact.

Lifespan

Around 8-10 years with good care - a genuinely long-lived fish and a near-decade commitment to a large animal, though averages of about five years are also cited when care is mediocre. What shortens it is predictable: an undersized tank that stunts and stresses the fish, poor or unstable water given the high bioload, an all-protein diet (a frugivore needs vegetables, and beef heart causes problems), and disease secondary to chronic stress.

Common mistakes

• Underestimating adult size and bioload. A cute juvenile becomes a roughly 20 cm, heavy-waste fish fast - do not buy unless you can give it about 55 gallons for one, or 75-plus for a pair or community.
• Mistaking "placid for a big cichlid" for "peaceful community fish." It is gentle relative to an oscar, not safe with tetras, rasboras or shrimp, which become food.
• Putting it in a planted aquascape. Soft live plants get eaten and uprooted; use java fern, anubias or hardscape instead.
• Feeding an all-protein diet. A frugivore needs a vegetable-forward menu; avoid beef heart and liver, which cause bloat.
• Species confusion at the till. "Severum" is a trade umbrella over several Heros taxa - the gold severum is the same species as green, while true H. severus and the mouthbrooding H. liberifer are different fish.

Signs of trouble

• Faded colour, clamped fins and hiding - general stress, often from an undersized tank or unstable water.
• Scraping or flashing with white spots - ich, usually after a chill or water-quality lapse.
• Pits and erosions on the head and lateral line - hole-in-the-head, linked to poor water, stale water and an over-protein or unvaried diet.
• Bloating and digestive trouble - too much fatty animal protein; switch to a vegetable-forward diet.
• A small tankmate that has simply vanished - it was almost certainly eaten; recheck that every tankmate is too big to swallow.

Is this fish right for you?

Do not buy a green severum if you cannot give it the tank it needs - about 55 gallons for a single adult and 75-plus for a pair or community. Do not buy it for a tank of small fish, shrimp or delicate nano species, which it will eat or outclass, and do not buy it if a pristine live-plant aquascape is the goal, because soft plants get mowed down. It is also not safe with large, aggressive cichlids that will bully the milder severum, nor ideal with persistent fin-nippers that harass its slow, deep body. Do buy it if you want a hardy, characterful, gentle-for-its-size centrepiece with robust, size-matched companions. On stock, prefer captive-bred fish: Wikipedia flags possible wild overexploitation given rising demand and naturally low population densities.

Common questions

How big does a green severum get?

About 20 cm (8 in) is the realistic adult size, with large, well-kept fish reaching around 25 cm. FishBase lists 17 cm standard length, which is roughly 20-22 cm total length. The frequently-quoted 30 cm figure is the rare wild maximum, not a typical aquarium adult, so plan around 20 cm.

Are green severums aggressive?

They are fairly mild-mannered for a cichlid of this size, and disputes rarely cause serious injury - but they are still large, semi-aggressive fish, not peaceful nano community fish. A lone fish or settled pair is usually calm; maturing and breeding fish can turn territorial around a spawning site.

Do severums eat other fish and plants?

Yes to both. They will eat any fish small enough to fit in their mouth, so small tetras, Boraras and shrimp are food, and they mow down soft live plants like a lawnmower. Keep them with robust, size-matched tankmates and use tough plants such as java fern and anubias or hardscape.

Are green severums mouthbrooders?

No - the green severum (Heros efasciatus) is a substrate spawner with biparental care. The confusion comes from a separate, mouthbrooding fish long mislabelled "H. severus" and renamed H. liberifer in 2015, which is why many old guides wrongly call severums mouthbrooders.

What tank size and tankmates does a green severum need?

Around 55 gallons for a single adult and 75-plus for a pair or community, with a long footprint and gentle flow. Good tankmates are robust, medium-to-large, non-aggressive fish it cannot swallow - silver dollars, larger characins, blue acara, size-matched angelfish, plecos and other catfish - not small fish, shrimp, big aggressive cichlids or persistent fin-nippers.

Sources & confidence

Sources & confidence (9 species)

These back the Green Severum figures and the previewed tank mates above. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

• Green Severum Heros efasciatus — Seriously Fish (seriouslyfish.com/species/heros-efasciatus) high confidence
• Boesemani Rainbowfish Melanotaenia boesemani — Seriously Fish; Aquarium Co-Op Boesemani guide high confidence
• Bristlenose Pleco Ancistrus sp. — Aquarium Source / aqua-fish.net Ancistrus care guides high confidence
• Keyhole Cichlid Cleithracara maronii — Seriously Fish (seriouslyfish.com/species/cleithracara-maronii) high confidence
• Molly (Common / Sailfin) Poecilia sphenops / Poecilia latipinna — Aquarium Co-Op molly care guide / FishBase Poecilia latipinna high confidence
• Moonlight Gourami Trichopodus microlepis — Seriously Fish (seriouslyfish.com/species/trichopodus-microlepis) high confidence
• Pearl Gourami Trichopodus leerii — Seriously Fish (seriouslyfish.com/species/trichopodus-leerii) high confidence
• Rubber Lip Pleco Chaetostoma formosae — Aquariadise (aquariadise.com/rubber-lip-pleco); Fish Laboratory medium confidence
• Scissortail Rasbora Rasbora trilineata — Seriously Fish (seriouslyfish.com/species/rasbora-trilineata) high confidence

Care-guide sources (7)

This guide synthesises the references below; where they disagree, the range and the disagreement are noted in the text above. The figures in the key-facts box are read from the TankStocking species database (v2026.06). Full welfare model on the methodology page.

• FishBase - Heros efasciatus
• Seriously Fish - Heros efasciatus (Severum)
• Wikipedia - Heros efasciatus
• Wikipedia - Banded cichlid (Heros severus)
• AquariumStoreDepot - Severum Cichlid Care Guide
• aqua-fish.net - Severum (Heros efasciatus)
• Staeck & Schindler (2015) - new Heros description / H. severus rediscovery

More on Green Severum

Related guides on TankStocking — each scored by the same welfare engine as the planner.

This care guide is a sourced planning reference, not veterinary advice — individual fish, filtration and maintenance all matter. Cycle the tank, test your water, and observe your fish. How TankStocking works →