Convict cichlid

Quick facts

Adult size

13 cm

Lifespan

can live up to 10 years; extremely hardy; specimens routinely live 8-10 years

Tank zone

all

Temperament

aggressive

Difficulty

beginner

Water parameters

Temperature

20–28°C

pH

6.5 to 8.5

Hardness

5 to 25 dGH

Tank requirements

Minimum volume

150 L

Minimum length

90 cm

Flow

low

Lighting

dim preferred

Substrate

any

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: omnivore, feeds primarily at the all.

Eats anything. Flake, pellets, frozen bloodworm, frozen brine shrimp, frozen mysis, live food, blanched vegetables, algae wafers. One of the least picky freshwater fish in the hobby. They forage constantly, picking at substrate, decor, and any organic matter they find. Feed twice daily. A varied diet keeps coloring at its best but convicts will thrive on a staple pellet diet with minimal supplementation. Overfeeding is common because they always act hungry and beg at the glass whenever someone approaches the tank.

Compatibility

• One of the most aggressive small cichlids when breeding, which is most of the time. A breeding pair in a 100-liter tank will terrorize everything else in it. The aggression is territorial and escalates once eggs are laid.
• Can be kept as a single specimen in a community tank with medium-sized robust fish, where it's only mildly territorial. The problems start when a pair forms. If you have a male and female in the same tank, assume they'll breed and plan accordingly.
• Good tankmates for a convict pair: other Central American cichlids of similar size (firemouth, salvini), large barbs, and catfish. Avoid small, slow, or delicate species. Convicts bully anything they can dominate.
• Hardy enough to serve as a 'starter cichlid' but the aggression during breeding catches new cichlid keepers off guard. The cute 3 cm juvenile in the store becomes a 12 cm territorial nightmare once it pairs up.

Habitat

Native to rivers and streams in Central America, from Guatemala south through Honduras, El Salvador, Nicaragua, Costa Rica, and Panama. Found in a range of habitats from fast-flowing rocky streams to still pools and lake margins. The species (Amatitlania nigrofasciata) is one of the most adaptable cichlids known: it tolerates hard water, soft water, pH from 6 to 8, temperatures from 20 to 30°C, and moderate levels of pollution that would stress most fish. This adaptability has made it an invasive species in warm waterways outside its native range, including parts of Australia, Japan, and the southern United States. In the aquarium, the classic wild-type has a gray body with 8-9 vertical black bars and a slight blue sheen on the scales. Females develop an orange-red patch on the belly during breeding. Several line-bred variants exist: pink (leucistic), calico, and long-finned forms. The pink variant is the most popular in stores. Adult size is 12–15 cm for males, 8–10 cm for females. The species has been in the hobby since the 1930s and is bred in enormous commercial quantities.

Breeding

Arguably the easiest cichlid to breed. A healthy pair in a tank with a flat stone or a cave will spawn without any conditioning, water chemistry manipulation, or special treatment. The female deposits 100-300 eggs on a flat surface (stone, pot, glass, driftwood) and both parents guard the clutch aggressively. Eggs hatch in 3-4 days. Fry become free-swimming in another 4-5 days and are shepherded around the tank by both parents. Parental care is intense and impressive: both adults defend the fry cloud against fish many times their size. Fry eat baby brine shrimp and crushed flake from day one. Growth is rapid. The challenge isn't getting convicts to breed but rather getting them to stop. A productive pair spawns every 3-4 weeks and rapidly overstocks any tank. Finding homes for the offspring is the real problem, because stores won't buy common convict cichlid fry and most hobbyists already have more than they want.

Common problems

Aggression during breeding is the primary management issue. A pair defending eggs or fry will attack anything in the tank, including fish twice their size. In community setups, this means constant stress and injury to tankmates. The simplest solution is a dedicated species tank for a breeding pair. If keeping them in a community, the tank needs to be large (200 L) with plenty of line-of-sight breaks. Hybridization with other Central American cichlids happens readily if multiple species are kept together; the resulting offspring are genetic mixes that are nearly impossible to rehome. Health problems are rare because convicts are among the hardiest aquarium fish. Ich, fin rot, and bacterial infections appear only under genuinely poor conditions. The species tolerates medication well. Overpopulation from uncontrolled breeding is the most common logistical problem keepers face.

Bioload

Bioload coefficient: 4.5 (robust mid-size cichlid; high waste output, comparable to a large goldfish proportionally).

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