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
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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 support@furrydiary.app 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
Checked 2026-09-30. Text is written in our own words from these sources.