Yellow mystery wrasse

Where they come from

Yellow mystery wrasse show up around central Pacific reefs, think places like the Marshalls, Tahiti, and the Cook Islands. You usually see them weaving through coral heads and rock cracks in rubble zones. They are nosy little hunters that spend the day working the rock for tiny snacks.

Setting up their tank

Give them a rock maze. They are crevice specialists, not sand sleepers, so focus on a stacked, stable reefscape with lots of hidey-holes and overhangs. They wedge into the rock at night and feel safer if they can duck out of sight quickly.

• Tank size: 55 gallons or larger. You can do 40 if the rockwork is generous and tankmates are mellow, but bigger is easier.
• Cover: tight lid or 1/4 inch mesh. They will jump. Not maybe. They will.
• Flow: moderate with calmer pockets around the rockwork.
• Lighting: anything reef standard. They do not care about PAR, your corals do.
• Substrate: sand is fine, but they do not bury. Bare-bottom works too if the rock is secure.
• Mature rock: a seasoned tank with pods makes the first few weeks smoother.

Basic parameters they handle well: 75-79 F, 1.024-1.026 salinity, pH 8.1-8.4, steady alkalinity. They are not drama queens, but they sulk with big swings.

What to feed them

They are micro-crustacean hunters by nature, so think small, meaty foods. Start with movement to get their attention, then mix in prepared stuff once they are settled.

• Frozen: mysis, enriched brine, finely chopped PE mysis, copepods, baby krill.
• Prepared: 0.5-1 mm marine pellets, quality reef blends, calanus.
• Live treats: live blackworms or live pods help new arrivals start eating.

Feed small portions 2-3 times a day at first. Once they are confident and picking at the rock, you can drop to 1-2. They will graze between meals.

How they behave and who they get along with

Think semi-bold ninja. They start shy, then one day they are front and center at feeding time. They are peaceful with most fish that ignore them, but they do not like lookalike wrasses. One Pseudocheilinus per tank is the safe play.

• Good tankmates: clowns, gobies, blennies, basslets, anthias, tangs, larger cardinals.
• Use caution: other wrasses, especially six-lines and four-lines. Someone will get chased.
• Inverts: generally fine with snails and hermits, but small ornamental shrimp (sexy, anemone, tiny peppermints) may become snacks. Full-size cleaner shrimp are a maybe, not a promise.
• Corals: safe. They do not nip corals. They might pick at feather dusters or small fan worms.

Breeding tips

They are protogynous wrasses that pair up and release pelagic eggs at dusk in the wild. In home aquariums, you are unlikely to see it, and raising the larvae is a whole project with specialized foods and separate systems. If you are curious, you can try a very large, peaceful tank and a well-matched pair, but most hobbyists keep them singly.

Common problems to watch for

• Jumping: number one cause of loss. Lock down the lid before the fish goes in.
• Wrasse wars: similar-shaped wrasses or a cranky six-line can turn this fish reclusive. Add last, and reshuffle rock if needed to break line-of-sight.
• Hunger strike on arrival: offer live or moving foods first, reduce flow at feeding, and keep people away from the glass for a few days.
• Parasites: like most wrasses, they can carry flukes. A proper quarantine and a round of praziquantel works well.
• Medication sensitivity: they handle treatments better than some delicate wrasses, but go slow with copper and watch appetite.
• Picking at shrimp: if you love tiny shrimp, skip this species or accept the risk.