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: destroys most plants.

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 severums in the aquarium trade are Heros efasciatus, not the true Heros severus. H. efasciatus is native to the Amazon basin, widespread throughout the main Amazon channel, the Rio Solimoes, and the Rio Xingu. H. severus is restricted to the upper Orinoco drainage in Colombia and Venezuela and the upper Negro basin. Described by Heckel in 1840; the genus Heros currently contains five recognized species. Found in calm, deeper, slow-moving rivers and tributaries, as well as tannin-stained floodplain lakes, usually near submerged branches and tree roots in dimly lit water. One of the few cichlid species that regularly eats plant matter as a significant part of its diet. Wild adults can reach about 30 cm (12 inches), though 20–25 cm (8-10 inches) is more typical in captivity. The wild green form has an olive body with dark vertical bars and iridescent green-blue speckling on the face. Multiple color variants have been line-bred: gold severum (the most popular; the gold trait is recessive, meaning both parents must carry the gene), red-spotted severum, and "super red". An undescribed form, Heros sp. "Rotkeil" (red shoulder), is thought by hobby specialists to represent a separate species. Lifespan approximately 10 years. Among the most peaceful of the larger South American cichlids outside of breeding season.

Breeding

Open substrate or flat-surface spawner. Pairs form lasting bonds and share parental duties. The breeding pair cleans a flat rock, piece of driftwood, or section of glass and the female deposits 200-800 eggs in neat rows. Both parents fan the eggs and remove fungused ones. Eggs hatch in 3-4 days. Fry are moved to a pre-dug pit in the substrate by the parents. Free-swimming fry feed on the parents' body mucus for the first few days (similar to discus), then graduate to baby brine shrimp and micro food. Both parents defend the brood aggressively. The parental behavior is one of the main reasons people keep severums: watching a bonded pair raise fry is compelling. In community tanks, the aggression during breeding is intense and other fish need enough space to retreat. Breeding is not difficult if the pair is compatible; the challenge is getting a compatible pair, as severums can be choosy. Buying a group of 6 juveniles and letting them pair naturally is the standard approach.

Common problems

Hole-in-the-head disease (HITH/HLLE) is the most common ailment in severums and other large New World cichlids. Symptoms: pits and erosions on the head and lateral line. Caused by a combination of poor water quality, vitamin/mineral deficiency, and possibly Hexamita parasites. Prevention: clean water, varied diet with vegetables, and regular water changes. Treatment: metronidazole for the parasitic component, dietary improvement for the nutritional component. Intestinal bloating from high-protein diets is the other common issue; keep the diet vegetable-heavy. Severums eat or uproot plants, which frustrates keepers who want a planted tank. Tough plants on hardscape (anubias, Java fern, Bolbitis) survive; stem plants and carpeting plants don't last.

Bioload

Further reading

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