Diamond tetra

Quick facts

Adult size

6 cm

Lifespan

can live up to 6 years

Tank zone

mid

Temperament

peaceful

Difficulty

beginner

Schooling

recommended 8+ (critical minimum 6, thrives at 10+)

Water parameters

Temperature

22–28°C

pH

5.5 to 7.5

Hardness

2 to 15 dGH

Tank requirements

Minimum volume

110 L

Minimum length

90 cm

Flow

low

Lighting

moderate

Substrate

any

Driftwood

preferred

Hiding spots

needed

Open swimming room

needed

Lid

required - jumper

Feeding

Diet: omnivore, feeds primarily at the mid.

Omnivore that eats anything. Flake, pellets, frozen bloodworm, frozen brine shrimp, frozen daphnia, live food, blanched vegetables. Feeds in the midwater column. Not picky and not demanding. A varied diet with regular frozen food improves the iridescent scaling and the dorsal fin extension in males. Feed twice daily. In community tanks they're moderately competitive and get their share without bullying.

Compatibility

• Peaceful schooling tetra that gets along with most community fish. Males develop impressively long dorsal fins and intense iridescence, making a mature group one of the more visually striking tetra displays available.
• Groups of 6+ are necessary for the best display. Males compete for female attention by spreading their dorsal fins and flashing their scales, which drives the iridescence to maximum intensity. Fewer than 6 and the behavior is muted.
• Slightly larger and more robust than most common tetras (5–6 cm), so they hold their own with medium community fish: barbs, rainbowfish, gouramis, and small cichlids. Not suitable with very small nano species that might be intimidated.
• The reflective scales are the defining feature. Each scale contains guanine crystals that create a diamond-like flash under light. The effect is strongest under warm-toned lighting from the side or above.

Habitat

Native to Lake Valencia and surrounding coastal river drainages in north-central Venezuela. The natural habitat is shallow, warm water with moderate vegetation. Lake Valencia itself has suffered significant environmental degradation (pollution, introduced species, water level fluctuations), and wild populations of the diamond tetra have declined. The aquarium trade relies entirely on commercially bred stock, which has been available since at least the 1930s. The body is covered in reflective guanine crystals that create a brilliant diamond-sparkle effect under light. Mature males develop a dramatically elongated dorsal fin that arches upward when displayed. The body color is silver with a violet to green iridescent sheen. Males are more intensely colored and have longer fins; females are fuller-bodied and slightly less reflective. Adult size is 5–6 cm. The species (Moenkhausia pittieri) is underrated in the hobby because store specimens are usually juveniles that haven't developed the full iridescent scaling or the dorsal fin extension. Adult males in breeding condition are among the most attractive common tetras available, but you'd never guess that from looking at them in a dealer tank.

Breeding

Egg scatterer. Males in breeding condition display intensified iridescent scaling and fully extended dorsal fins. Condition a pair with frozen food for 7-10 days. The breeding tank should have soft, slightly acidic water (pH 6.0-7.0, GH below 8), fine-leaved plants or spawning mops, and dim lighting. Temperature at 26–27°C. Spawning typically occurs at dawn. The pair scatters 200-400 eggs among the plants. Eggs are semi-adhesive. Adults eat eggs aggressively, so remove them immediately after spawning. Eggs hatch in 24-36 hours. Fry are small and need infusoria for the first 3-4 days before graduating to baby brine shrimp. Growth is moderate; the reflective scaling begins to develop at about 6-8 weeks. Dorsal fin elongation in males doesn't become apparent until the fish is 3-4 months old and doesn't reach full development until well past a year. This slow maturation of the display traits is why store-bought juveniles look so different from established adults.

Common problems

Juvenile ugliness is the main reason this species is overlooked. Diamond tetras in stores are small, pale, and unremarkable. They develop their full beauty over 6-12 months. Keepers who buy them expecting instant impact are disappointed. The fix is patience. Health-wise, they're hardy. Ich appears in stressed new fish; standard treatment works. The iridescent scaling loses intensity in tanks with bright overhead lighting and pale substrate. Dark substrate, subdued lighting, and tannin-stained water produce the most impressive visual effect. Water quality tolerance is good; they handle a moderate range of pH and hardness. Lifespan is 5-7 years. Older fish develop the most impressive dorsal fins and scaling.

Bioload

Bioload coefficient: 0.8 (mid-sized tetra; slightly higher than neon due to larger adult size).

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