Tanaka's possum wrasse
Wetmorella tanakai
Tanaka's possum wrasse exhibits a striking pattern of vibrant blue and green scales, with a distinctive elongated body and a prominent dorsal fin.
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About the Tanaka's possum wrasse
A tiny, secretive reef wrasse that slips through rockwork and picks at micro-crustaceans, Tanaka's possum wrasse brightens a tank with sharp white bars and bold false eyespots. It stays small and is very gentle, but it does best in a calm, mature reef with lots of caves and food-rich nooks.
Also known as
Quick Facts
Size
5 cm TL (about 2 inches)
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
15 gallons
Lifespan
3-6 years
Origin
Southeast Asia
Diet
Carnivore - small benthic invertebrates; accepts frozen mysis, enriched brine, and other finely chopped meaty foods
Water Parameters
22-26°C
8.1-8.4
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This species needs 22-26°C in a 15 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give a single Tanaka's possum wrasse at least 15 gallons in a calm, mature reef with lots of caves and tight rockwork to weave through.
- Hold temperature at 22-26 C and pH at 8.1-8.4; stable, clean marine water keeps this small wrasse settled.
- Feed small meaty foods it accepts readily, like frozen mysis, enriched brine, and finely chopped marine fare, and let some food drift into crevices for this shy picker.
- They graze on tiny micro-crustaceans in the rockwork, so brand-new, sterile tanks can leave them hungry; mature, food-rich nooks make a big difference.
- Stick with peaceful tankmates; boisterous or aggressive fish will outcompete or stress this gentle, secretive species.
- They are reef safe with corals and spend most of their time slipping through rockwork rather than bothering polyps.
- Expect about 3-6 years with good care; the challenge is their secretive nature and preference for a settled, low-drama reef.
Compatibility
Good Tankmates
- Small, peaceful gobies (neon gobies, clown gobies, Eviota/Trimma species) that perch and do not compete hard at feeding time
- Firefish/dartfish (Nemateleotris spp.) that are calm midwater swimmers and unlikely to bully shy wrasses
- Small cardinalfish (Banggai or pajama cardinals) that are gentle, slow, and reef-safe
- Tiny, non-aggressive blennies like the tailspot blenny that graze algae and ignore the wrasse
- Another very small, gentle wrasse such as a pink-streaked wrasse, only in a larger, rock-filled tank and added together
- Reef-safe inverts (cleaner/peppermint shrimp, snails, small hermits); the wrasse hunts micro-crustaceans, not ornamental shrimp
Avoid
- Aggressive or pushy wrasses like six-line and other Pseudocheilinus that will harass a shy possum wrasse
- Dottybacks and similarly territorial cave-dwellers (Pseudochromis, aggressive basslets) that compete for the same rockwork
- Boisterous or territorial clowns and damsels that dominate space and outcompete at feeding, especially in small tanks
- Large or predatory fish (groupers, lionfish, hawkfish) and very fast feeders that intimidate or potentially prey on tiny wrasses
Tanaka's possum wrasse (Wetmorella tanakai) is a tiny, secretive reef fish from Southeast Asia. It slips through rockwork, picking at micro-crustaceans, and shows off sharp white bars with bold false eyespots. Gentle and small, it does best in a calm, mature reef with lots of caves and food-rich nooks.
Quick facts
- Size: up to 5 cm TL (about 2 inches)
- Temperament: peaceful
- Care level: intermediate
- Lifespan: 3-6 years
- Minimum tank: 15 US gallons
- Temperature: 22-26 C
- pH: 8.1-8.4
- Diet: carnivore (small benthic invertebrates; accepts frozen mysis, enriched brine, and finely chopped meaty foods)
Origin and natural habitat
Native to Southeast Asia, this species is a cryptic reef wrasse that spends most of its time close to the rockwork. In the wild it threads through tight crevices and overhangs, picking tiny crustaceans from hard surfaces and rubble.
Aquarium setup and water conditions
A peaceful, mature reef tank of 15 gallons or more suits this fish. Provide a maze of live rock with caves, cracks, and shaded pockets so it can retreat and hunt between feedings. It does best in calm communities rather than high-activity layouts.
- Temperature: 22-26 C
- pH: 8.1-8.4
- Aquascape: complex rockwork with multiple hideouts and food-rich nooks
- Lighting/flow: standard reef conditions; avoid chaotic environments that push timid fish into hiding
Add Tanaka's possum wrasse to a well-established tank. Mature live rock with healthy microfauna makes settling in easier for this small, shy hunter.
Diet and feeding
In nature it eats tiny benthic invertebrates. In the aquarium it usually accepts frozen mysis, enriched brine shrimp, and other finely chopped meaty foods. Offer small portions the fish can swallow whole.
- Feed small amounts 2-3 times daily to offset competition from faster fish
- Rotate finely chopped meaty items; use enriched options for better nutrition
- A mature tank lets the fish pick at micro-crustaceans between meals
Behavior and tankmates
This is a very peaceful, retiring wrasse. It spends much of the day working the rockwork and will duck into caves when spooked. Pair it with calm, non-aggressive tankmates that will not outcompete it at feeding time.
- Good context: small, gentle reef fish that do not harass shy species
- Avoid: boisterous or aggressive fish and notably fast feeders that monopolize food
- Keep only one per small tank if similar-sized wrasses cause shyness or food competition
Common problems and how to avoid them
- Failure to settle in new tanks: place in a mature system with established rockwork and natural microfauna.
- Starvation from competition: offer multiple small feedings and distribute food so timid fish get their share.
- Chronic hiding due to stress: provide abundant caves and avoid pushy tankmates so the fish feels secure.
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