Severum

Quick facts

Adult size

20 cm

Lifespan

can live up to 10 years

Tank zone

middle

Temperament

semi-aggressive

Difficulty

intermediate

Water parameters

Temperature

24–30°C

pH

5.5 to 7.5

Hardness

2 to 15 dGH

Tank requirements

Minimum volume

300 L

Minimum length

120 cm

Flow

moderate

Lighting

moderate

Substrate

sand

Driftwood

preferred

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: omnivore, feeds primarily at the middle.

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.

Vegetable matter required (algae wafers, blanched zucchini, spinach).

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.

Habitat

Native to the Amazon River basin and its tributaries across Brazil, Colombia, Peru, and the Guianas. Found in slow-moving, vegetated waterways and flooded forests during the wet season. The wild form (Heros efasciatus) has a greenish-olive body with dark vertical bars and a dark spot on the gill cover. Multiple color variants have been bred in captivity: gold severum (bright yellow-gold), red severum (orange-red body), green severum (iridescent green on the standard olive base), and super red (deep orange). The gold severum is the most popular in the hobby, followed by the red. Adults reach 20–25 cm and live 8-10 years. The species has been in the trade since the 1970s. The common name comes from the Latin "severus" (severe or stern), referring to the fish's serious expression from the dark facial markings. Body shape is deep and laterally compressed, similar to a discus but heavier-built.

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

Bioload coefficient: 10.0 (20 cm heavy cichlid with substantial waste output).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

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