Jawfish - Dusky

Aquarium Requirements

Minimum Tank Size: 110 litres (30 US gallons)

Temperature: 24–27 °C (75–81 °F)

pH: 8.1–8.4

Specific Gravity (Salinity): 1.020–1.025

Alkalinity: 8–12 dKH

Ammonia & Nitrite: 0 ppm

Nitrate:< 10 ppm

Substrate and Aquascape:
A deep sand bed (minimum 7–10 cm / 3–4 inches) of fine aragonite mixed with small shell rubble is essential for burrow construction. Provide scattered rocks or coral rubble pieces to reinforce the burrow structure. The aquascape should include open sandy areas for burrowing and moderate rock formations for security.
Moderate water flow and excellent oxygenation are recommended. A tight-fitting lid or mesh cover is mandatory, as jawfish are known jumpers—especially when startled.

Diet and Feeding

The Dusky Jawfish is carnivorous, feeding primarily on small crustaceans, plankton, and zooplanktonic prey in the wild. In captivity, it accepts a variety of frozen and live foods once acclimated.

Recommended Foods:

• Frozen mysis shrimp, enriched brine shrimp, finely chopped krill, and small crustaceans

• Copepods and amphipods (ideal for natural feeding behaviour)

• High-quality marine carnivore pellets or small frozen blends

• Occasional live foods to stimulate feeding and maintain condition

Feed 2–3 times daily in small portions, ensuring food reaches the fish near its burrow. The Dusky Jawfish may initially be shy, so target feeding with a pipette or baster can help during acclimation.

Temperament and Compatibility

The Dusky Jawfish is peaceful and shy, preferring to stay close to its burrow. It is territorial toward other jawfish but non-aggressive toward dissimilar species. Once established, it will display endearing curiosity, often peeking from its burrow or rearranging substrate.

Suitable Tankmates:

• Peaceful reef fish such as gobies, small wrasses, firefish, and clownfish

• Shrimp, snails, and other small, non-aggressive invertebrates

Avoid:

• Large or aggressive fish that may intimidate or disturb it (e.g. triggers, groupers, or large wrasses)

• Other jawfish species unless the tank is large enough to support multiple territories

Reef Compatibility

✅ Reef Safe

The Dusky Jawfish is entirely reef safe and poses no threat to corals, invertebrates, or clams. However, it may occasionally move loose coral frags or small rubble while excavating its burrow, so ensure coral bases are secure on the substrate.

Additional Information

Maximum Size: 10–12 cm (4–5 inches)

Lifespan: 5–7 years in captivity with good care

Difficulty Level: Moderate (requires deep sand bed and secure lid)

Natural Behaviour: Burrow-building, substrate rearranging, cautious but inquisitive

Origin: Western Atlantic – Caribbean Sea, Bahamas, and Gulf of Mexico

Colouration: Pale tan to dusky brown body with subtle mottling; darker shading along dorsal surface and lighter ventral side; large expressive eyes

Summary

The Dusky Jawfish (Opistognathus whitehursti) is a captivating, reef-safe burrow dweller admired for its personality and naturalistic behaviour. Best kept in aquariums with a deep sand bed and stable water conditions, it rewards aquarists with engaging, territorial displays and endearing burrow-guarding habits. With appropriate care, the Dusky Jawfish adds both character and ecological depth to the marine aquarium.