Six Line Wrasse (Pseudocheilinus hexataenia)

What is a Six Line Wrasse?

The Six Line Wrasse (Pseudocheilinus hexataenia) is one of the most eye-catching small fish available for a saltwater aquarium — and one of the most popular for good reason. Six bold, horizontal stripes of electric blue alternating with orange-red run the full length of the body, complemented by a vivid false eye-spot near the tail that fools predators into misjudging which end to attack. The total package is under 8 cm (about 3 inches), which makes the intensity of the colouration genuinely startling.

Beyond the looks, the Six Line earns its place as a working member of a reef community. It actively hunts pyramidellid snails, monogenean flatworms, and other small parasitic hitchhikers that can devastate clams and corals. That pest-control role is not incidental — it is one of the main reasons reef keepers add this species specifically.

The trade-off is temperament. The Six Line Wrasse starts life as a curious, relatively peaceful fish and can become progressively bolder and more territorial as it matures. It rarely causes serious damage to larger tank-mates, but it will harass smaller, more passive fish — sometimes relentlessly. Choosing compatible neighbours and adding the wrasse last in the stocking order goes a long way toward keeping the peace.

Where do Six Line Wrasses come from?

Wild Six Line Wrasses are found across an enormous range of Indo-Pacific reefs — from the Red Sea and East Africa east through the Indian Ocean and Pacific, reaching as far as the Line Islands, and from southern Japan south to the Great Barrier Reef in Australia. Within that range they occupy shallow, rubble-strewn reef slopes and coral heads, typically at depths of 1–30 metres, darting through gaps in the live rock and coral structure in search of tiny invertebrate prey.

They are consistently caught in that shallow-to-mid-depth rubble zone, which tells you exactly what kind of environment to replicate: established live rock with plenty of caves, crevices and overhangs, and a sand substrate for sleeping.

What size tank and setup does a Six Line Wrasse need?

The recommended minimum is 110 litres (approximately 29 US gallons), but this is genuinely a minimum and not a comfortable long-term size. A 200-litre or larger system suits this fish better, gives territory breathing room, and makes it far easier to maintain stable reef chemistry.

Setup priorities:

• Live rock structure. Provide a complex reef scape with caves, tunnels and overhangs. The Six Line actively patrols rockwork hunting prey and needs secure hiding spots to feel safe.
• Sand bed. A fine aragonite sand bed of at least 5 cm depth is strongly recommended. Six Line Wrasses are wrasse-typical sand-sleepers — they bury themselves at night and may also dive in when stressed. Without a sand bed they resort to wedging into rock, which increases stress and abrasion injuries.
• Covered tank. This species is an excellent jumper. A tight-fitting lid or cover is not optional.
• Mature system. The Six Line does best in an established reef of at least three to six months, where natural microfauna populations — copepods, amphipods, small worms — supplement the diet. A bare, newly cycled tank provides very little for it to hunt.

What water parameters does a Six Line Wrasse need?

Like all reef fish, the Six Line Wrasse requires stable, high-quality saltwater parameters:

• Salinity: 1.023–1.025 SG (specific gravity); natural seawater is around 1.025. Avoid the lower “fish-only” salinities used in FOWLR tanks — keep it reef-standard if corals are present.
• Temperature: 24–27 °C (75–81 °F).
• pH: 8.0–8.4, ideally stable and not swinging over the day-night cycle.
• Ammonia / Nitrite: 0 ppm. Non-negotiable.
• Nitrate: below 10 ppm for a reef; the Six Line tolerates somewhat higher levels without immediate harm, but elevated nitrates stress the system as a whole.
• Calcium / Alkalinity / Magnesium: keep within standard reef ranges if corals are present (Ca ~400–450 ppm, dKH 8–11, Mg ~1250–1350 ppm).

Stability is more important than perfect numbers. Sudden salinity shifts, temperature swings or a pH crash are more immediately dangerous than a parameter sitting slightly outside the textbook optimum. Use a quality refractometer (not a swing-arm hydrometer), a reliable heater with a backup, and a regular testing schedule.

What do Six Line Wrasses eat?

The Six Line Wrasse is a dedicated carnivore with a strong prey drive for small invertebrates. In the wild it feeds on tiny crustaceans, worms, snails, and parasitic invertebrates. In captivity it typically accepts:

• Frozen mysis shrimp — the staple; most specimens accept this readily.
• Frozen brine shrimp (enriched preferred) — good variety item, lower nutritional value than mysis alone.
• Frozen copepods and amphipods — excellent, mimics natural diet closely.
• High-quality carnivore pellets or flake — many individuals learn to accept these, though some refuse prepared foods indefinitely.
• Live copepods / amphipods — ideal for a newly introduced or reluctant feeder; a refugium seeding copepod populations into the display tank is a significant quality-of-life upgrade.

Feed twice daily in small amounts. A fish that forages actively on live rock between feedings is eating well; a fish that only hides during feeding and shows no interest in hunting suggests poor acclimation or water quality issues.

Is the Six Line Wrasse reef safe — and what can live with it?

Yes, it is reef safe in the standard sense: it will not eat corals, and it actively eliminates certain pests (pyramidellid snails, flatworms) that harm clams and corals. Most reef keepers consider this a net positive.

The nuances worth knowing:

• Ornamental shrimp: Large cleaner shrimp (Lysmata amboinensis, L. debelius) are usually tolerated. Tiny ornamental shrimp — Sexy Shrimp, Peppermint Shrimp juveniles, very small Camelback Shrimp — are at risk.
• Small passive fish: Dartfish, tiny gobies, small cardinalfish, and mandarin dragonets can be harassed persistently. The Six Line will not usually kill a healthy, mobile tank-mate, but it will bully fish that cannot or will not flee.
• Good companions: Other semi-aggressive reef fish of similar or larger size — clownfish, medium-sized tangs, larger dottybacks, hawkfish, moderately assertive gobies, gramma — coexist well in a properly sized tank. Larger, confident fish tend to simply ignore the wrasse.
• Conspecifics: One per tank in all but the very largest systems. Two Six Lines will fight; if you want a pair, introduce a confirmed male-female pair simultaneously into a large tank (400+ litres).

Add the Six Line last when stocking: establishing territory after all other inhabitants are already settled significantly reduces aggression.

How do you tell male and female Six Line Wrasses apart?

Difficult in most cases. Males are generally larger and may display slightly more intense colouration, but there is no single reliable visual marker under home-tank conditions. The Six Line Wrasse is a protogynous hermaphrodite — individuals begin life female and the dominant fish in a group transitions to male. In the home aquarium, where a single specimen is kept, the fish may function as male or female depending on social conditions, and you are unlikely to be able to confirm sex without observing spawning behaviour.

For practical purposes: buy one, assume you cannot determine its sex, and do not attempt to keep a second specimen hoping for a breeding pair unless you are working in a large, purpose-built system.

How do Six Line Wrasses breed?

Breeding in captivity is very rarely achieved and rates as very hard. In the wild, spawning is a brief daily event at dusk: a male and female rise together in the water column and release gametes simultaneously. The fertilised eggs are pelagic (free-floating) and hatch into larvae that spend weeks in open water before settling.

Replicating the trigger cues, achieving consistent pair spawning, and raising the planktonic larvae through to metamorphosis requires specialised equipment, very fine live foods (copepod nauplii), and expertise that goes well beyond standard reef keeping. Occasional spawning attempts have been reported in large home systems, but successful rearing to juvenile stage remains essentially uncharted territory for hobbyists.

What are common Six Line Wrasse health problems?

The Six Line Wrasse is a hardy reef fish when kept in stable, mature conditions, but it is susceptible to the same diseases that affect other marine fish:

• Marine ich (Cryptocaryon irritans): The most common reef disease — white spots resembling grains of salt on the skin and fins. Stress (shipping, incompatible tank-mates, poor water quality) lowers immunity. Treatment in a reef tank is complicated because copper-based medications kill invertebrates; hyposalinity or tank transfer method are standard options in a quarantine system.
• Marine velvet (Amyloodinium ocellatum): More aggressive than ich; fish appear to have a fine gold or rust-coloured dust. Moves fast — isolate and treat promptly.
• Uronema marinum: A ciliate that can infect stressed or injured fish, particularly those held at low salinity or kept in suboptimal conditions post-import. Best prevented by thorough quarantine of new arrivals.
• Fin damage / abrasion: Often caused by stress-related hiding in tight rock crevices, especially in tanks without a sand bed. Provide a deep sand bed to reduce this.

Quarantine all new fish for 4–6 weeks in a dedicated quarantine tank before adding them to a display reef. This single step prevents the majority of disease introductions that would otherwise require treating an entire system.

How long does a Six Line Wrasse live?

A well-kept Six Line Wrasse typically lives 4–6 years in a home aquarium, and possibly longer in exceptionally stable, well-managed systems. Because most specimens are wild-caught and of unknown age at import, the clock may already be running when you purchase the fish — but buying a sub-adult or small juvenile gives you the best chance at the full lifespan.

The variables that most influence longevity are water stability, stress levels, and feeding quality. A fish in a mature, stable reef with good flow, regular varied feedings, and compatible tank-mates will consistently outlive one kept in a cramped, aggressive, or chemically unstable tank.