Six Line Wrasse Care Guide: The Reef-Safe Pest Controller

Species Overview#

The Six Line Wrasse (Pseudocheilinus hexataenia) is one of the most-recommended "utility" fish in the reef hobby. A reef keeper does not buy this fish because it is the prettiest in the tank, although the magenta body striped with electric blue and gold is striking. They buy it because it spends every waking minute hunting through the rockwork, picking off the small invertebrates that quietly eat corals and clams. For an intermediate hobbyist fighting flatworms, pyramidellid snails, or red bugs, a Six Line Wrasse is often the cheapest answer to a problem that would otherwise cost hundreds of dollars in dips and treatments.

The trade-off is temperament. A Six Line Wrasse the size of a finger can run a 75-gallon reef like a tyrant — chasing new additions, harassing similar-bodied fish, and occasionally turning on the very ornamental shrimp the keeper hoped to coexist with. This guide walks through where the species belongs, where it does not, and how to set the tank up so the bargain works in your favor.

Adult size

3 in (7.5 cm)

Lifespan

4-6 years

Min tank

30 gallons

Temperament

Semi-aggressive

Difficulty

Intermediate

Diet

Carnivore (pest picker)

Identifying Pseudocheilinus hexataenia: The six horizontal stripes#

The common name is literal. Six narrow horizontal stripes — usually orange-gold against a magenta-to-purple body — run head to tail along each flank. The dorsal half of the body sits closer to violet, while the belly fades to peach. The eye is bright red and the caudal fin shows a green-yellow base. Adult coloration is fixed; juveniles look like miniature adults rather than going through a separate color phase. There is no reliable visual sexing in the home aquarium.

If a fish at the store has fewer than six stripes, faded barring, or stripes that wash into the background, walk past it. Color saturation is the single best on-the-spot indicator of condition.

Natural habitat: Indo-Pacific coral rubble zones#

Wild populations span a huge range — from the Red Sea east to the Tuamotu Islands, north to southern Japan, and south to the Great Barrier Reef. They prefer the lagoon side of reefs, in coral rubble and live rock at depths of roughly 6 to 100 feet. They do not school. A wild fish patrols a small territory, weaving in and out of crevices in search of copepods and amphipods.

That habitat is what to copy at home: dense, interconnected rockwork with multiple swim-throughs and tight caves. Open sand flats with a single bommie of rock will not satisfy them.

Maximum size (3 inches) and typical lifespan (4-6 years)#

Six Line Wrasses top out around 3 inches in captivity. In the wild they can reach 4 inches but rarely do so in a home aquarium. Lifespan in a stable reef is typically 4 to 6 years. Most premature deaths trace back to either jumping out of an open-top tank or starving in a sterile system that lacks the live copepods they prefer to graze on between feedings.

Water Parameters & Tank Requirements#

Six Line Wrasses are not the most parameter-sensitive marine fish, but they live inside a reef ecosystem, so reef-grade water is the standard.

Minimum tank size: Why 20-30 gallons is the absolute floor#

A Six Line Wrasse can survive in a 20-gallon nano, but a 30-gallon tank with mature rock is a more honest minimum. Below that volume, three problems compound: the wrasse runs out of pod stock to graze on within weeks, its territorial aggression covers the entire tank with no neutral zones, and any other fish becomes a target. A 40-gallon breeder with a refugium feeding pods into the display is the sweet spot for a single specimen and a few peaceful tank mates.

Reef builders looking for a similar-footprint reef-safe alternative often compare this species with the orchid dottyback, which fills the same "small magenta predator" niche with a different temperament profile.

Ideal parameters: Temp (72-78°F), pH (8.1-8.4), Specific Gravity (1.024-1.026)#

Aim for the standard reef numbers and hold them steady:

• Temperature: 72-78°F (22-26°C)
• pH: 8.1-8.4
• Specific gravity: 1.024-1.026 (1.025-1.026 matches natural seawater)
• Ammonia and nitrite: 0 ppm
• Nitrate: under 10 ppm for a coral-heavy system, under 20 ppm for FOWLR

Stability matters more than the exact target. A tank that drifts between 78°F and 82°F daily stresses fish more than one that sits at a steady 80°F.

The importance of rockwork and hiding caves#

A Six Line Wrasse needs three things from its rockwork: cover for sleeping, ambush points for hunting, and enough surface area to cultivate a healthy copepod population. Build the aquascape with plenty of overhangs, tunnels, and shelves. Avoid stacking rock as a single solid wall against the back glass — the fish needs to swim around and through it. A mature live rock system that has been seeded with pods and bristleworms gives the wrasse something to do all day; a freshly cycled tank with bare ceramic rock will leave it bored and hungry within a month.

Jump-proofing: Why a tight-fitting lid is non-negotiable#

Like most wrasses, Pseudocheilinus hexataenia will jump when startled. A loose pellet hitting the surface, a sudden shadow, or a turf war with a tank mate is enough to send the fish onto the floor. A tight-fitting glass lid or a screen top with no gaps is the only reliable prevention. Mesh screen kits (such as those from BRS or DIY versions using window screen and corner brackets) are the standard solution for open-top reefs because they preserve light penetration without sacrificing security.

Diet & Feeding#

This species is a strict carnivore and a constant grazer. Treat feeding as supplementation to natural foraging, not as a replacement for it.

Natural foraging: Hunting for copepods and amphipods#

In the wild and in a healthy reef tank, a Six Line Wrasse spends most of its day picking copepods, amphipods, isopods, bristleworm eggs, and small crustaceans out of the rockwork. A tank with a refugium full of chaeto algae feeding pods into the display will keep the wrasse busy and well-fed without requiring heavy supplemental feeding. This natural foraging is also what makes the species effective at pest control — the same hunting behavior that picks copepods also picks pyramidellid snails and red bugs.

Supplemental feeding: Mysis, brine shrimp, and high-quality flakes#

Feed once or twice daily in small portions. A solid rotation:

• Frozen mysis shrimp (the staple — most six lines accept it within hours of being added to the tank)
• Frozen brine shrimp enriched with selcon or similar HUFA supplement
• Cyclop-eeze or other small frozen zooplankton blends
• High-quality marine pellets (New Life Spectrum AlgaeMax or similar) for variety
• Occasional live black worms or live brine for stubborn eaters

Avoid bulk flake-only diets. Six Line Wrasses fed exclusively on flake food fade in color within months and live noticeably shorter lives. If the fish refuses prepared food in the first few days after introduction, it is usually because the rockwork is full of pods — wait it out and offer food again in a few days.

Pest control: Their role in eating flatworms and pyramidellid snails#

This is the headline reason most reef keepers buy the species. A motivated Six Line will systematically clear:

• Red planaria flatworms (the rust-colored ones that smother frags)
• Pyramidellid snails (the white parasitic snails that drain clams and snails)
• Acropora red bugs (Tegastes acroporanus) on SPS colonies
• Bristleworm eggs and very small bristleworms

What it will not reliably eat: the larger Polyclad flatworms that prey on snails, full-size bristleworms, or aiptasia anemones. Match the tool to the pest before assuming this fish solves every reef problem.

Tank Mates & Compatibility#

This is where most Six Line Wrasse projects succeed or fail. The fish is small, but its personality is not.

Managing aggression: Why they should be the last fish added#

Add the Six Line Wrasse last. Always. Once it claims a territory in an established tank, anything new is a trespasser. If the wrasse is the resident and a new fish arrives, the wrasse will harass the newcomer relentlessly. If a new fish is the resident and the wrasse arrives last, the resident has the upper hand and the wrasse has to negotiate space.

In tanks under 40 gallons, expect the Six Line to dominate the entire system. In larger tanks (75 gallons and up) with broken aquascaping, multiple fish can carve out separate zones and coexist peacefully.

Reef-safe status: Corals vs. ornamental shrimp/crabs#

Six Line Wrasses are reef safe with corals. They will not nip at LPS, SPS, soft corals, zoanthids, or clams. The asterisk is invertebrates. Larger ornamental shrimp like cleaner shrimp and most peppermint shrimp are usually safe, but smaller or newly molted shrimp are at risk. Sexy shrimp and pom-pom crabs frequently end up as snacks. Small feather dusters can also be picked at when the wrasse is hungry.

Incompatible species: Avoiding other small wrasses and shy bottom-dwellers#

Tank mates to avoid:

• Other Pseudocheilinus species (eight line, four line)
• Small fairy and flasher wrasses under 4 inches
• Shy gobies that compete for the same crevices (Hi-Fin gobies, some shrimp gobies)
• Mandarin gobies in tanks under 75 gallons (the wrasse will outcompete the mandarin for pods)
• Small or juvenile additions of any species in tanks under 40 gallons

Tank mates that work well:

• Captive-bred clownfish pairs
• Royal grammas (more on the royal gramma)
• Yellow tangs and other surgeonfish in larger tanks
• Cardinalfish (Banggai, pajama)
• Sturdy gobies like yellow watchman or diamond gobies
• Most blennies

Sleep behavior: Mucus cocoons in rockwork, not sand#

Worth stating plainly because it surprises new keepers familiar with Halichoeres species: the Six Line Wrasse does not bury itself in sand at night. It picks a crevice in the rockwork, spins a thin mucus cocoon around itself, and sleeps wedged into the rock. This means a deep sand bed is not required for the species, but high-quality rockwork is.

Common Health Issues#

Six Line Wrasses are hardier than many marine fish but still susceptible to the standard reef parasites.

Marine Ich and Velvet susceptibility#

Marine ich (Cryptocaryon irritans) shows as discrete white spots on the body and fins. Marine velvet (Amyloodinium ocellatum) shows as a fine gold or rust-colored dust over the skin and is far more lethal — it can kill a Six Line Wrasse within 48 hours. Both require copper treatment in a separate quarantine tank, never in the display reef. This is why every new Six Line Wrasse should spend 4 weeks in quarantine with prophylactic copper before going into the display.

Internal parasites and "stringy white poop"#

Wild-caught Six Line Wrasses frequently arrive with internal parasites picked up during the collection and shipping chain. The clinical sign is stringy, white, mucus-coated feces — sometimes hanging from the fish for hours. Treat with metronidazole-soaked food (Seachem MetroPlex mixed with a binder like Focus into a paste, then coated onto frozen mysis). A two-week treatment course usually clears the infection.

Mouth injuries from glass surfing or rock scraping#

A stressed Six Line will sometimes ram the front glass repeatedly during the first few days in a new tank. This can scrape the mouth raw, leading to secondary bacterial infection. Dim the room lights for 48 hours after introduction, drape a towel over the front glass, and avoid feeding heavily until the fish settles. If the mouth shows redness or fungal cotton, a freshwater dip followed by quarantine treatment with kanamycin is the standard response.

Where to Buy & What to Look For#

Captive-bred Six Line Wrasses are not yet commercially available, so every specimen on the market is wild-caught. That makes selection at the store especially important.

Selecting a vibrant, active specimen at your LFS#

Pick a fish that is constantly in motion. A Six Line Wrasse that is hovering in one spot or hiding listlessly in the corner of the tank is almost always a poor candidate. Coloration should be saturated — magenta body, bright orange-gold stripes, red eye. Faded color on the body is a stress sign and often signals a fish that will not eat or recover.

Ask the staff to feed the fish in front of you. A healthy specimen will hit the food within seconds. A fish that ignores food at the store is unlikely to start eating once it gets to your tank.

Signs of a healthy "hunter" (constant eye movement)#

Acclimation#

Use a slow drip acclimation. Float the bag for temperature equalization (about 15 minutes), transfer the fish and bag water to a clean container, then drip tank water in at a rate of 2-3 drops per second until the volume has tripled. Net the fish into the quarantine tank — never pour the bag water in. Total acclimation time should run about 60-90 minutes. For more on the general method, see the acclimating fish guide.

After acclimation, the fish goes into a 4-week quarantine with prophylactic copper at therapeutic levels, then into the display tank.

Quick Reference#

• Tank size: 30 gallons minimum, 40+ gallons recommended
• Temperature: 72-78°F
• pH: 8.1-8.4
• Specific gravity: 1.024-1.026
• Diet: Carnivore — frozen mysis, brine, and live pods from rockwork
• Tank mates: Clownfish, royal gramma, cardinalfish, sturdy gobies, blennies, tangs in larger tanks
• Avoid: Other small wrasses, sexy shrimp, pom-pom crabs, small/juvenile additions in small tanks
• Difficulty: Intermediate — easy to keep but tricky to integrate into a community
• Special note: Sleeps in rockwork (no sand bed required), needs a tight-fitting lid

Reef builders interested in alternative pest controllers and tank mates should also look at the orchid dottyback (semi-aggressive but pellet-trained captive-bred lines exist) and the royal gramma (peaceful purple-and-yellow basslet that fills a similar visual role without the wrasse's aggression). For broader reef setup planning, see the saltwater aquarium guide and the saltwater fish overview.