Care guide · Freshwater · fish

Green severum

Heros efasciatus

Heros efasciatus. Photo: Klaus Rudloff, Wikimedia Commons, CC BY-SA 4.0. Photo: Klaus Rudloff / CC BY-SA 4.0 (via Wikimedia Commons) · Source · CC BY-SA 4.0Wikimedia 960px thumbnail and site-generated responsive resized/converted derivatives; derivatives are provided under CC BY-SA 4.0 with attribution and license link.

Heros efasciatus is a large Amazonian cichlid commonly called a severum in the aquarium trade. It is relatively mild-mannered for its size outside spawning, but adults need substantial floor space and may eat smaller fish. This guide covers source-based aquarium and water ranges, layout, feeding and reproduction. The trade name severum is also applied to other Heros fish, so a shop label alone does not guarantee an exact identification. We also explain why a frequently repeated mouthbrooding claim needs careful checking, and we avoid unverified tankmate or product recommendations.

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At a glance

Temperature: 22.2–28.9 °C
pH: 5.5–7.0
GH: 1–8 °dGH
Aquarium length: At least 120 cm
Minimum aquarium volume: At least 243 L
Adult size: Up to 30 cm
Group size: At least 1 individuals
Temperament: Peaceful, Territorial

About this species

Eschmeyer's Catalog of Fishes recognizes Heros efasciatus Heckel, 1840 as a valid species in Cichlidae. The aquarium name severum has historically been used broadly for several related Heros species and colour forms. A green or gold shop strain therefore cannot be assigned to an exact population or lineage on colour alone. Heros appendiculatus appears in older name history, but the accepted species name is H. efasciatus. Reported size is not consistent across sources. Seriously Fish gives a maximum of 30 cm standard length (SL) and says aquarium adults often reach 20–25 cm. FishBase lists a smaller recorded maximum, and a field study measured fish up to 17.4 cm SL. Because the sources and settings differ, plan space using the larger aquarium-profile figure rather than treating a smaller observation as a fixed adult size. SL measures the body without the caudal fin.

Natural habitat

The species occurs in the Amazon basin, including quiet tributaries, rivers and floodplain lakes. Seriously Fish lists the Amazon main channel and Solimões, with records from the Xingu; the California Academy of Sciences gives a basin-wide range across several countries. Many habitats include submerged tree roots and branches in deeper, slow-moving water. A reproductive study from the Amanã reserve describes riparian vegetation, flooded areas and calm water as relevant environments. This background can help explain the value of cover, but it is not a fixed aquarium blueprint. Sand, sturdy roots and subdued light are consistent with the specialist care profile. There is no need to add peat or leaf litter if it complicates water quality or maintenance; stable conditions and usable refuge matter more.

Aquarium and layout

Seriously Fish specifies a minimum of 120 × 45 × 45 cm and approximately 243 litres. Length and base depth matter for this deep-bodied cichlid; a taller tank with the same volume does not necessarily provide the same usable floor area. It is therefore unsuitable for small aquariums. Use sand, a few sturdy roots or branches, and subdued lighting. The aquarium source says aquatic plants were not a feature of its natural waters, but that alone does not prove every plant is unsuitable. We link no individual plant here without a separate species-specific assessment. Use reliable biological filtration and leave open swimming space. Check rocks and wood for stability, especially if fish disturb the substrate. The source gives a minimum setup, not a universal stocking density. Remember that additional fish increase waste and territorial interactions; do not decide stocking by litres per fish alone.

Water conditions

The aquarium profile gives 22.2–28.9 °C, pH 5.5–7.0 and GH 1–8 °dGH. This describes soft, acidic to mildly acidic aquarium water. These ranges are source tolerances, not a reason to swing quickly between endpoints. Choose a stable setup suitable for the fish’s provenance and make changes gradually. The source does not provide a reliable KH range, so no KH figure is shown. A reproductive field study reports different temperature and pH context for natural sites. Measurements from field research are not direct aquarium targets and do not replace the species-specific aquarium profile. Mature the filter, test ammonia and nitrite, and make regular water changes. For a large, actively fed fish, sufficient filtration and consistent maintenance are essential.

Behaviour and group size

Outside spawning, the severum is described as relatively mild-mannered for its size. A pair may defend its spawning site. The species can eat smaller fish, so shared temperature or pH does not prove a safe match. The source mentions large, peaceful South American fish only as a broad possibility, not as individually checked companions. We therefore publish no specific tankmate links. Assess adult size, swimming zone, social needs and available space before combining species. Some individuals may become more aggressive when kept alone; the care source suggests that conspecifics can often reduce this, but it gives no exact minimum group size. Raising juveniles together may allow a pair to form, but requires a larger aquarium and a plan for surplus fish. Males grow larger, may show markings on the gill covers and a nuchal hump, and may develop longer dorsal and anal fins. Juveniles cannot be sexed reliably by appearance.

Feeding

Heros efasciatus is omnivorous. Seriously Fish recommends quality dried food alongside animal supplements such as bloodworm, chopped earthworm and prawn, plus plant matter. Shelled peas, blanched spinach and spirulina-based foods are named in the profile. The field study also describes the species as omnivorous and mainly frugivorous in flooded forest. Vary the diet, offer portions that are eaten, and remove leftovers. The existing product catalogue has no food that is both approved specifically for this species and supported by a fresh, usable offer. No product card is shown. Do not choose food only because its title says “cichlid” or “algae”; also check the composition, pellet size and whether the fish readily eat it.

Breeding

The reliable evidence supports substrate spawning: eggs are laid on a flat stone or root and both parents care for eggs and larvae. A group of juveniles may be raised until a pair forms. Provide a suitable spawning surface and room to defend it, and monitor other inhabitants closely while the pair is breeding. Parents may move or guide larvae after hatching, but that does not establish mouthbrooding. Seriously Fish says both parents carry the fry in their mouths. This conflicts with FishBase, which describes eggs on stones or roots and parental care of eggs and larvae, and with the reproductive study of H. efasciatus. The 2015 specialist taxonomic description identifies the unusual mouthbrooding Heros as H. liberifer, not H. efasciatus. We therefore do not present mouthbrooding as a care fact for this species. The field study reports a seasonal pattern in one Amazon region; it is not a guaranteed aquarium breeding calendar.

Sources & review

This care guide draws on several specialist sources and was last checked on 17 October 2026.

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