Not furry, but we like them anyway.
McCosker's Flasher Wrasse
Paracheilinus mccoskeri
Also called McCosker's flasher
From Indian Ocean and Indo-West Pacific: from East Africa through Thailand and northern Sumatra, with records east to Fiji12
A friendly guide, not veterinary advice. For anything about your pet's health, ask your vet.
At a glance the quick version
Looks how to spot one
Small, slender reef wrasse; males have extended dorsal fin rays
A small, colourful wrasse in shades of red, orange, yellow and blue. Males are brighter than females and carry long filaments on the dorsal fin, which they raise and 'flash' when showing off to females.13
Personality what they are like
Peaceful and social. Males put on a show for females by intensifying their colours and spreading their fins.31
Daily activity how busy a day looks
An active swimmer that often stays close to the bottom and moves around in small groups; males dart from place to place.31
Grooming and care the hands-on bits
Use a tight-fitting lid, as flasher wrasses are known to jump. Keep one male per tank with several females.3
Home where they are happiest
A reef aquarium of at least 55 US gallons (about 210 L) with rock and open swimming room. Saltwater at about 22 to 26 °C, pH 8.1 to 8.4, specific gravity 1.020 to 1.025, dKH 8 to 12. In the wild it lives on outer reef slopes over rubble, algae or coral at about 5 to 50 m, in water of 25 to 28 °C.31
Food basics what goes in the bowl
A carnivore. Offer enriched frozen mysis and brine shrimp, other meaty foods, and quality marine flakes and pellets.31
Company who they like around
Lives in small groups where females far outnumber males. Best kept as one male with a harem of females.13
The story where it all began
John E. Randall and Mireille Harmelin-Vivien described the species in 1977. Both its common and scientific names honour the American ichthyologist John E. McCosker, who collected the type specimens and supplied the colour photographs used for the description.21
Fun facts for the dinner table
- 1
The 'flasher' name comes from the way males suddenly spread and flash their fins to impress females.3
- 2
The species is named after ichthyologist John E. McCosker, who collected the first specimens.2
- 3
In the wild, groups contain many more females than males, with the males patrolling around them.1
- 4
Juveniles are often seen alone or in small groups among reef rubble.1
Recognised by the official bits
- IUCN Red List
- Least Concern (assessed 2009)1
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a McCosker's Flasher Wrasse. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Salinity checkevery week
- Top-upTop up evaporation with fresh RO water, not salt waterevery day
- Water testevery week
- Water changeAbout 10 to 20% of the waterevery 2 weeks
- Glass cleanevery week
Owner questions the things everyone asks
How often should I feed my McCosker's Flasher Wrasse?
Furry Diary's starting plan is to offer small amounts once or twice a day. This carnivore will thrive on enriched frozen mysis and brine shrimp, plus quality marine flakes and pellets. Adjust portions based on what your fish eats in a couple of minutes, and ask your vet or a good breeder for specific amounts.31 Furry Diary plan
What does a McCosker's Flasher Wrasse eat, and what should it never eat?
It's a carnivore that enjoys enriched frozen mysis and brine shrimp, other meaty foods, and quality marine flakes and pellets. Never feed it anything that isn't meant for marine carnivores, and avoid overfeeding. For exact amounts, check the food label and consult your vet.31
How much space does a McCosker's Flasher Wrasse need?
A reef aquarium of at least 55 US gallons (about 210 L) is recommended, with plenty of rock and open swimming room. This active swimmer needs space to dart around, so a larger tank is even better for a small group.31
What temperature, light or water does a McCosker's Flasher Wrasse need?
Keep saltwater at 22 to 26 °C, pH 8.1 to 8.4, specific gravity 1.020 to 1.025, and dKH 8 to 12. Furry Diary's plan suggests checking temperature daily, salinity weekly, and doing a 10-20% water change every two weeks. Use a tight-fitting lid as they can jump.31 Furry Diary plan
How often should I clean a McCosker's Flasher Wrasse's home?
Furry Diary's starting plan includes cleaning the glass weekly, testing water weekly, and changing 10-20% of the water every two weeks. Top up evaporation daily with fresh RO water, not salt water. Regular cleaning keeps your wrasse healthy and happy. Furry Diary plan
Can a McCosker's Flasher Wrasse live with others?
Yes, it's peaceful and social, living in small groups where females far outnumber males. Best kept as one male with a harem of several females. It can share a reef tank with other non-aggressive fish, but avoid housing two males together.31
How long does a McCosker's Flasher Wrasse live?
Lifespan varies depending on care and environment. With a proper diet, stable water conditions, and a stress-free home, they can live several years. For a more precise estimate, ask your vet or a good breeder.
Can I handle a McCosker's Flasher Wrasse?
It's best not to handle this fish, as it's delicate and easily stressed. They are active swimmers that prefer to stay in the water. If you need to move it, use a soft net gently and avoid touching its body.31
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Furry Diary's own starting care plan. A friendly guide, not a vet's advice.
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.
- FishBase: Paracheilinus mccoskeri, McCosker's flasher fishbase.seused for distribution, size, depth, temperature, habitat, behaviour, IUCN status, describers
- Wikipedia: Paracheilinus mccoskeri en.wikipedia.orgused for distribution, size, etymology, history
- LiveAquaria: McCosker's Flasher Wrasse liveaquaria.comused for aquarium care, tank size, water parameters, temperament, diet, display behaviour
- VCA Animal Hospitals: Feeding times and frequency for your dog vcahospitals.comused for owner questions
- ASPCA: Dog grooming tips aspca.orgused for owner questions
- ASPCA: Cat grooming tips aspca.orgused for owner questions
- ASPCA: People foods to avoid feeding your pets aspca.orgused for owner questions
- RSPCA: What to feed your rabbit rspca.org.ukused for owner questions
Checked 2026-09-30. Text is written in our own words from these sources.