Severum

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: sand.

Behavior

Plant interaction: plant ripper.

Feeding

Omnivore with a strong vegetarian component. Spirulina-based pellets, algae wafers, blanched peas, blanched zucchini, blanched spinach, and romaine lettuce are the plant-based staples. Supplement with frozen bloodworm, frozen shrimp, and frozen krill 2-3 times weekly. They eat plants in the tank; live plants will be damaged or uprooted unless they're tough species like anubias or Java fern attached to hardscape. Feed once or twice daily. Overfeeding leads to bloating because the herbivorous gut ferments excess protein. A plant-heavy diet prevents most digestive issues.

Compatibility

• Large, relatively calm cichlid that coexists with similarly sized fish. In the cichlid world, severums are considered mellow, which means they still defend territory during breeding and will eat anything small enough to fit in their mouth.
• Tankmates should be medium to large: larger tetras (silver dollars, buenos aires), catfish (bristlenose, raphael), loaches (clown), and other moderate cichlids. Avoid small fish; anything under 5 cm is potential food for an adult severum.
• Pairs form strong bonds and both parents guard eggs and fry cooperatively. During breeding, they become aggressive toward everything in the tank, including fish twice their size.
• Often recommended as a "beginner cichlid" for keepers moving up from community fish. The temperament is manageable and the care requirements are simpler than similar-sized New World cichlids.

Origin and habitat

Most fish sold as severums are Heros efasciatus, not the true Heros severus they are often labelled as. H. efasciatus is widespread in the Amazon, through the main channel, the Solimoes, and the Xingu, while the true severus lives in the upper Orinoco and upper Negro and is a mouthbrooder, a different reproductive style from the substrate-spawning efasciatus. Heckel described severus in 1840, and the genus Heros now holds several species across the Amazon, Orinoco, and Essequibo. Severums are large, deep-bodied, relatively calm cichlids of slow, deep, tannin-stained waters with submerged wood. Unusually for a cichlid, a good part of the diet is plant matter, so they tend to eat or uproot soft aquarium plants. Wild fish can reach about 30 cm, with 20 to 25 cm more usual in a tank. The wild green form is olive with dark bars and green-blue facial speckling, and the trade offers line-bred colours including the popular gold severum, whose gold is a recessive trait, plus red-spotted and super-red strains; the red-shoulder or Rotkeil form is a distinctive variant that some specialists treat as a separate undescribed species.

Breeding

An open substrate spawner that forms strong, lasting pairs with shared parental care. The pair cleans a flat rock, a piece of wood, or the glass and the female lays a large clutch, several hundred up to around a thousand eggs, in neat rows, and both parents fan the eggs and pick off any that fungus. The eggs hatch in two to three days, the parents move the fry to a pit, and for the first days the free-swimming fry graze mucus from the parents' bodies much as baby discus do before taking baby brine shrimp. Both parents guard the brood hard. Breeding is not difficult once a compatible pair forms, but severums can be choosy, so the usual route is to raise a group of six and let a pair sort itself out.

Common problems

Hole-in-the-head is the classic ailment of severums and other big New World cichlids, showing as pits and erosion along the head and lateral line; it is tied to poor water quality, a thin or vitamin-short diet, and the Hexamita parasite, so the defences are clean water, a varied vegetable-rich diet, and regular changes, with metronidazole and better feeding to treat an active case. Bloating from too much protein is the other common problem, again answered by a plant-heavy diet. And because they eat and uproot plants, a planted severum tank only really works with tough species like anubias, java fern, and Bolbitis anchored to hardscape.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size