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
This is one of those tiny, sneaky reef wrasses that basically lives in the rockwork and pops out to hunt little micro-bugs all day. The red-orange body with thin white bars and those little "eye spots" on the fins make it a really cool "where did that fish come from?" kind of addition. It is super peaceful, but it does best in a mature reef where it can graze and not get pushed around.
Also known as
Quick Facts
Size
6 cm (2.4")
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
25 gallons
Lifespan
3-6 years
Origin
Western Pacific
Diet
Carnivore/micro-predator - pods and other micro-invertebrates, tiny live foods, enriched brine shrimp, cyclops, mysis; some may take flake
Water Parameters
23-27°C
8.1-8.4
8-12 dGH
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This species needs 23-27°C in a 25 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a rock-heavy tank with lots of little caves and overhangs - it spends most of its time weaving in and out of cracks, and it gets jumpy in bare setups.
- Cover the tank tight. Possum wrasses can and will launch through tiny gaps when spooked, especially at lights-out or during a chase.
- Keep salinity stable around 1.020-1.025 and temperature in the mid-70s F (about 23-27°C); they do best with steady numbers and a mature, stable system.
- Feed small meaty stuff 1-2 times a day: mysis, enriched brine, calanus, chopped clam, and good micro pellets once its eating well. If it ignores food at first, try live pods or live baby brine to get it started, then mix in frozen.
- Peaceful tankmates only - think gobies, firefish, smaller basslets, and calm clowns. Skip dottybacks, big wrasses, hawkfish, and anything that likes to bully shy fish out of the rocks.
- Pods help a lot, so a mature tank or refugium is a nice safety net, especially while its settling in. They will pick at the rock between meals and stay fuller and calmer with a steady pod supply.
- Watch for it slowly fading away from not getting enough food - they can look fine but lose weight if faster fish outcompete them. Target feed near its cave and turn down flow for a minute during feeding if you have to.
- Breeding in home tanks is rare; they are harem spawners in the wild and eggs/larvae are tiny pelagic stuff. If you ever see a pair doing quick dusk rises, thats the closest you are likely to get without a serious larval setup.
Compatibility
Good Tankmates
- Small, peaceful reef fish like clownfish (the calmer ocellaris/percula types) - Tanaka's possum wrasse mostly just scoots around the rockwork and ignores them
- Firefish and dartfish (Nemateleotris spp.) - similar vibe, peaceful, and they keep to their own lanes if you give them hiding spots
- Neon gobies, clown gobies, and other small gobies (Elacatinus, Gobiodon) - they co-exist great in a reef and neither one is looking for a fight
- Blennies that are not mean about territory (tailspot blenny, bicolor blenny in a roomy tank) - good rock-perchers that usually leave the possum wrasse alone
- Small flasher or fairy wrasses (Paracheilinus, Cirrhilabrus) - active but typically not bullies, and the possum wrasse just stays in the nooks and cruises for pods
- Peaceful small cardinals like banggai or pajama cardinals - mellow midwater fish that do not hassle shy wrasses
Avoid
- Dottybacks (especially orchid dottyback) - they love the same rockwork and caves, and the dottyback tends to out-attitude a possum wrasse fast
- Hawkfish (flame hawk, longnose hawk) - perch-and-pounce types can harass a shy possum wrasse and stress it out in smaller setups
- Big or pushy wrasses (sixline, fourline, melanurus, coris types) - they get territorial and the possum wrasse usually loses that game
- Aggressive tank bosses like triggers and most larger damsels - too much chasing and chaos for a little possum wrasse that just wants to pick at tiny critters
Where they come from
Tanaka's possum wrasse (Wetmorella tanakai) is one of those tiny, secretive reef wrasses that lives in the nooks and crannies of coral-rich areas. Think tight rockwork, rubble, and lots of shadows where small crustaceans hang out. In the tank, they act the same way - they want cover and they want to hunt.
Setting up their tank
If you give this fish a big open aquascape, you'll barely see it. Give it a rock maze and it turns into a little gremlin that peeks out all day. My best success with possum wrasses has been in mature tanks with lots of micro-life and plenty of hiding places.
- Tank size: 20+ gallons works, but more rock and stability beats raw gallons
- Rockwork: tight caves, overhangs, and rubble zones they can weave through
- Flow: moderate; give them calm pockets behind rocks where they can hover
- Lighting: anything reef-standard; they do appreciate shaded areas
- Lid: cover the tank - they can jump, especially early on or when spooked
Build at least one "escape tunnel" in the rockwork (a continuous route through caves). They relax a lot once they learn they can disappear without getting pinned in a corner.
I treat them like a shy goby more than a flashy wrasse. A calm tank, stable salinity, and a bit of age on the system goes a long way. They are not a fish I would use to break in a brand new reef.
What to feed them
These guys are small-predator pickers. In my tanks they spend the day inspecting rock and coral bases for tiny snacks. The main challenge is getting a new one eating in a busy community tank where food gets annihilated in 10 seconds.
- Best starters: live copepods, live baby brine, live blackworms (if you can get them clean), enriched frozen cyclops
- Reliable frozen: mysis (smaller pieces), brine shrimp plus enrichment, finely chopped krill, calanus, fish roe
- Prepared foods: some will take small pellets or soft micro foods, but I wouldn't count on that at first
Target feed with a baster or pipette near their favorite cave. If you just broadcast feed, your tangs and clowns will eat for them and the possum wrasse will slowly fade.
Small meals more often beats one big dump of food. I aim for 2-3 feedings a day for the first couple weeks, then you can settle into whatever your tank can handle as long as the fish keeps a nice, rounded belly.
How they behave and who they get along with
Tanaka's possum wrasse is peaceful and a bit spooky. It moves in short hops, freezes a lot, and will vanish if a bigger fish gets pushy. Once it's settled, you'll see it cruising the rockwork like it's on patrol.
- Good tankmates: small, calm reef fish (gobies, blennies, firefish in a peaceful tank, small cardinals), cleaner shrimp, most corals
- Avoid: aggressive dottybacks, big wrasses, hawkfish, triggerfish, puffers, and any "food-first" bullies
- Caution: larger shrimp and crabs are usually fine, but tiny ornamental shrimp (very small sexy shrimp, tiny juveniles) could be at risk
They can get outcompeted easily. Even if nobody is biting them, a fast feeding frenzy can still starve them over time.
Reef-safe is the expectation here. They may snack on very small worms and pods (which is kind of the point), but I've never seen one bother corals or clams.
Breeding tips
Spawning in home tanks is not common, and raising the larvae is the hard part. Like many wrasses, they are pelagic spawners - eggs and larvae end up in the water column. In a mixed reef, that usually turns into "free coral food" pretty quickly.
If you ever see a quick upward dash at dusk followed by tiny specks in the water, you may have witnessed a spawn. A dedicated larval setup and live plankton cultures would be the next step, not the display tank.
Common problems to watch for
- Not eating after introduction: very common; solve with quiet surroundings, pod-rich rock, and targeted live/frozen foods
- Slow starvation: they look "fine" for weeks, then you notice a pinched belly and lethargy
- Jumping: usually in the first days or after a scare - a tight lid saves lives
- Harassment stress: they hide nonstop, breathe fast, and stop coming out for food
- Parasites (marine ich/velvet): wrasses can be touchy with harsh treatments; quarantine and observation are your friend
If a possum wrasse is breathing hard and parked in the open, don't wait it out. Check for bullying, ammonia issues, and obvious parasite signs right away. They are small fish and can go downhill fast.
The biggest key is patience. Give it cover, feed like you mean it (without turning the tank into soup), and keep the tank social scene mellow. Once they settle, they are hardy little characters and a really fun fish to spot throughout the day.
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