Six Line Wrasse Tank Mate Compatibility Guide: Aggression Map

Few reef fish split opinion like Pseudocheilinus hexataenia. The six line wrasse tank mates question matters because the species is genuinely useful — it eats pyramidellid snails, flatworms and bristleworms — yet it also turns into the tank tyrant within 18 months. This guide from Gensou Aquascaping at 5 Everton Park maps the aggression curve, lists fish that survive the pairing, and explains the stocking order that prevents most problems before they start.

The Aggression Timeline

Juvenile six lines (3-4 cm) are timid, hover around the rockwork and pose no threat. By six months they hit 5-6 cm and territorialise the upper rockwork. By 12-18 months a fully mature 8 cm specimen patrols the entire aquascape and chases anything entering its zone. The shift is gradual, then sudden — and once it kicks in, removing the wrasse means breaking down half the rockwork.

Stocking Order Is Everything

Add the six line wrasse last in the stocking sequence — after the blennies, gobies, clownfish, dottybacks and tangs are all settled. Established residents defend their territory from the newcomer rather than the other way around. Adding a six line first, even into a four-month-old reef, results in chronic stress for every later addition.

Safe Tank Mates

Larger tangs (yellow, kole, Naso, sailfin), powder blue tangs once acclimated, larger angels (Coral Beauty and up), big clownfish pairs, foxfaces and rabbitfish all tolerate or out-mass the wrasse. Cardinalfish hold their own through schooling. The relationship is rarely friendly but rarely catastrophic.

Risky Tank Mates

Other small wrasses — fairy wrasses, flasher wrasses, leopard wrasses, the related Pseudocheilinus tetrataenia four-line — almost always trigger aggression. The six line reads them as direct competitors and harasses them to exhaustion. Pink streaked wrasses, pelvic-spot wrasses and similarly sized peaceful labrids are particularly vulnerable.

No-Go Combinations

Skip pairing six lines with firefish, dartfish, small gobies under 5 cm and any small peaceful blenny. The wrasse harasses them at feeding time and into their burrows. Helfrichi firefish and purple firefish typically vanish into rockwork after the first chase and slowly starve. Yellow clown gobies do better because they sit motionless on coral, but expect occasional skirmishes.

Tank Size Threshold

Anything under 200 litres concentrates aggression too tightly. The six line wrasse needs sight lines blocked by 12-18 kg of rockwork, multiple swim corridors, and the visual buffer that a longer 90-120 cm footprint provides. Nano reefs of 60-100 litres are simply too small for the species past 12 months. Browse aquascape rock and tank options across the aquarium equipment range.

Females and Single Specimens Only

Keeping a pair almost always fails — the dominant fish kills the other within weeks. Pseudocheilinus hexataenia is a protogynous hermaphrodite, but you cannot reliably sex juveniles, so single specimens are the only safe rule. Specialist breeders occasionally sell mated pairs, but the success rate is poor without a 400-litre or larger system.

Reef and Invertebrate Compatibility

Six lines are reef safe with corals — they do not nip polyps and ignore SPS, LPS and softies entirely. Cleaner shrimp generally hold their own; the wrasse may chase fire shrimp briefly. Smaller ornamental shrimp like sexy shrimp and porcelain crabs sometimes get harassed. Expect snails to survive while small Trochus and Astraea graze openly.

Removal Strategies

Sooner or later many reefers need to remove an aggressive six line. Bottle traps work for the patient — bait with mysis, set overnight, retrieve in the morning. Breaking down rockwork to chase the fish stresses the entire system. The aquascaping tools range covers fish nets and bottle traps suitable for the job. Carousell rehoming usually finds takers within days at SGD 15-25.

Sourcing in Singapore

Iwarna, Aquamarin and Reef Discus Centre stock six lines regularly at SGD 28-45. Smaller juveniles handle quarantine better and integrate more smoothly into established reefs. Quarantine for two to four weeks and observe feeding response before adding to the display. Pair with quality marine flake and frozen mysis from the marine and saltwater range.

Related Reading

• Pink Streaked Wrasse Care Guide
• Red Coris Wrasse Care Guide
• First Year Reef Livestock Stocking Order Guide
• Reef Tank Readiness Checklist 30-Day Guide
• Yellow Clown Goby Care Guide