Oxymonacanthus longirostris OXYLON-101409-PEDMAT-001

This entry was posted on Wednesday, October 14th, 2009 and is filed under Filefishes, Spawning Reports.

Matthew W. Pedersen Breeder: Matthew W. Pedersen
Date posted: 10/14/2009

The Breeder’s Registry data contained in this report are taken from submitted observations from the aquarist unless otherwise noted (see comments). Information may be reproduced provided The Breeder’s Registry is cited.

Spawning Report for: Oxymonacanthus longirostris (Bloch & Schneider, 1801)

Reference used for scientific name: https://www.fishbase.in/summary/Oxymonacanthus-longirostris.html

Common names: Harlequin Filefish, Orangespotted Filefish, Longnose Filefish.

Geographic origin: Indo-Pacific



Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Tetraodontiformes
Family: Monacanthidae
Genus: Oxymonacanthus
Species: longirostris (Bloch & Schneider 1801)


Description: Body is pale blue with approximately eight rows of orange-yellow spots. Male has translucent orange coloration in soft portions of dorsal and anal fins.  Male’s ventral flap (pelvic rudiment) is bright orange-red with a think black border above, with several rows of fine white spots. Female’s dorsal/anal fins are 100% clear. Female’s ventral flap is black, with few if any fine spots.


Length of time in captivity: 1.5 yrs+

Size male (inches): 3″

Length of time in captivity female: 1.5 yrs+

Size female (inches): 3″

Adult diet: Enriched Frozen Brine Shrimp, Mysis Shrimp, Pellet and Flake Foods, Roe, chopped squid.

Feeding Frequency: 4 – 5 times/day.

Pre-spawning activity: There is elaborate courtship that can last for minutes or hours.  Noteable behaviors are the female “algae ramming”, that is, thrusting her face into various clumps of algae as if probing for spawning site suitability.  There is also the “flutter dive” performed by the male, and to a lesser extent, the female.  Spawning occurs VERY quickly, only a couple seconds where eggs are deposited into the algae.

Time of spawning:  varies with water temperature, typically in afternoon / evening hours.

Frequency of spawning:  Daily

Location of spawning: Typically in a patch of red Gracillaria

Description of Spawn:  Female moves vent to algae, male comes in and releases sperm as female releases eggs… female takes a few more seconds after…and that’s it.

Size of eggs (mm): 0.8 mm

Approximate quantity:  200

Eggs/larvae removed to a separate tank: Yes, eggs must be removed.

How:  Typically sucked out of the gracillaria immediately after spawning with the aid of a turkey baster.  Eggs are demersal and adhesive, with many (20+) oil globules.

Description of eggs/larvae:  Eggs develop over the next 2 days and hatch out as prolarvae with a bright green yolk sac.

Incubation period: 50 + hours after spawning

Time of hatching:  50+ hours after spawning

Larval attraction to light:  No



Capacity (Gallons): 24

DIMENSIONS: (Length): 19″ (Width): 19″ (Height): 18″

Tank side coverage:  Back is covered  Color: black

Filtration:  Mechanical, Chemical (Carbon) and Biological filtration.

Pumping volume (gph):  200+

Type of seawater used:  Reef Crystals

Frequency/Volume of changes:  Weekly, 25%, occasionally up to 50%



Specific Gravity: 1.025  Measured by: Refractometer

Source of Replacement Water: tap

pH: 8.1  Measured by: Seachem kit

Temperature (F):  upper 70’s to lower 80’s  Fluctuation: 3-4 degrees

Nitrates: 40 ppm  Measured by: Quick Test dip

Calcium: N/A

Additives, medications added:  Routine dosing with Reef Plus, Reef Calcium, Reef Buffer , Reef Builder, Reef Iodide.

Frequency and dose:  Per manufacturer instructions

PHOTOPERIOD (Spawning Tank):

Wattage: 72  Photoperiod: 14 hours



Size at Hatching: 2.7 mm or so

Yolk Sac: yes

First food offered: Rotifers, must be offered by 48 hours post hatch.

Frequency of feedings: Constant, using greenwater technique

Second food offered:  Baby Brine Shrimp  When: 21 days

Frequency of feedings:  baby brine ALWAYS present, with newly enriched nauplii added at least twice per day.

Third food offered: Otohime A pellets and Crushed Spirulina Flake, should start at 28 days

Larval food culture:   Standard

SURVIVAL: varies – ranges: week 1: 10 to 50%, week 2: 1 to 50%, week 3: 1 to 50%, week4: 1 to 25%

Long term survival:  Settlement occurs around 56 days post hatch, but can take longer.  Had juveniles well past 100 days and 5 months on a single individual, feeding on nothing but prepared foods.  Lost one long term survivor to a jump, and the other longest term survivor to Amyloodinium.  Future attempts should yield better results.  Proper weaning and early larval rearing are critical to long term viability.

Metamorphosis:  Metamorphosis is a long drawn out process.  Flexion occurs between 18 and 25 days.  Final settlement is at approximately 56 days, at which point the juveniles being sleeping on the substrate at night.


Grow-out feeding regimen:  Greenwater Technique.  Best Results with a 4 gallon Drum Style fishbowl converted into an air-driven kreisel, and heated via water bath in a 10 gallon tank.  Water chemistry was not measured.  Water changes up to 50% per day were made using water from broodstock reef in the earlier days, and clean fresh saltwater later on.

PHOTOPERIOD (Grow-out Tank):

Wattage: 15  Photoperiod: 24 hours (constant)


Other vernacular names: Orange-spot filefish, Beaked Leatherjacket

Original Description: First described by Bloch & Schneider in 1801 as Balistes longirostris hispidus variety in Systema Ichthyol.; ref. 471., from specimens collected in the East Indies. Valid as Oxymonacanthus longirostris by Hutchins, 1984.

Word origin: The genus Oxymonacanthus is from the Greek root(s) oxy meaning sharp; mon meaning single or one; and acanth meaning a spine or thorn;T tus a “sharp single spine” . The species longirostris is a fairly common descriptor from the Latin root(s) long, -i, meaning long; and rostrum meaning a beak or snout. When one looks at Oxymonacanthus longirostris the definition definitely “fits”!

Suggested reading:

A New Future for the Harlequin Filefish – CORAL, March/April 2009.

About this report: Information contained in this report is taken from submitted observations. Taxonomy, Synonomy, Original description , Word origin and Suggested reading are provided by member(s) of The Breeder’s Registry staff. Information is presented under the belief that it is accurate. If you have information in addition to, or contrary to, that which is presented you are encouraged to contact The Breeder’s Registry. Permission is granted for “one-time” personal use. Reproduction as distributed or accessible media is prohibited without prior written permission. Copyright © 2009 The Breeder’s Registry. All rights reserved.

Breeder's Registry staff are all volunteers and appreciate any comments or corrections on any of our posts.

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