Blue Dot Jawfish (Opistognathus Rosenblatti)

Photo by Rhododendrites, CC BY-SA 4.0, via Wikimedia Commons

Jawfish, Blue Dot (Opistognathus rosenblatti) – A Personality-Packed Burrow Builder

The Blue Dot Jawfish, Opistognathus rosenblatti, is one of the most entertaining and charismatic fish you can add to a saltwater aquarium. Known for its bright blue spots, expressive eyes, and comical hovering behavior above its burrow, this species quickly becomes a favorite centerpiece in smaller reef systems. With the right aquascape and sandbed, a Blue Dot Jawfish will reward you with constant activity and fascinating natural behavior.

Natural Behavior & Tank Requirements

In the wild, Blue Dot Jawfish inhabit sandy rubble zones where they construct elaborate burrows. Replicating this in your aquarium is essential to their health and longevity.

Tank Size & Aquascape

While the Blue Dot Jawfish doesn’t get very large (around 4 inches), it is active and needs floor space rather than height. A minimum 30-gallon tank is recommended, with a strong emphasis on a secure lid—these fish are notorious jumpers.

• Tank size: 30 gallons or larger, with plenty of open sandbed.
• Substrate: 3–4 inch mixed grain sandbed (fine sand plus some small rubble).
• Rockwork: Stable rock structures that won’t collapse when the fish digs beneath them.
• Lid: Tight-fitting mesh or solid cover to prevent jumping.

For more ideas on how to set up a stable reef foundation, see our guide on aquascaping live rock layouts.

Water Parameters & Compatibility

Blue Dot Jawfish are somewhat sensitive and do best in a mature, stable system. Aim for:

• Temperature: 72–76°F (cooler than many tropical reef species).
• Salinity: 1.024–1.026 specific gravity.
• pH: 8.1–8.4 with minimal daily swings.
• Nutrients: Low but not sterile; a well-cycled tank is essential.

They are generally peaceful but can be territorial with their own kind, especially in smaller tanks. Keep one per tank unless you have a large system and can provide multiple, well-spaced burrow zones. Avoid aggressive tankmates that may harass them or steal food.

Feeding, Care Tips & Long-Term Success

Jawfish spend much of their time near their burrows, so target feeding and appropriate food size are key.

Diet & Feeding Strategy

• Foods: Enriched mysis shrimp, finely chopped seafood, and high-quality marine pellets.
• Frequency: 1–2 times daily, in small amounts they can consume quickly.
• Technique: Use a turkey baster or pipette to gently deliver food near the burrow entrance.

Pro tip: Feed at roughly the same times each day. Blue Dot Jawfish quickly learn the schedule and will hover higher in the water column, making feeding easier.

Sandbed & Burrow Maintenance

Because their burrow is their home base, the condition of your sandbed directly impacts their comfort and stress level.

• Provide a mix of fine sand and small shells or rubble so they can reinforce their tunnel.
• Avoid overly powerful flow directly on the sandbed, which can collapse their burrow.
• Do not frequently disturb the area where your Jawfish has established its home.

If you’re planning a new tank specifically for burrowing species, check out our article on choosing sand and substrate for reef tanks.

Acclimation & Stress Reduction

Blue Dot Jawfish can be shy and stressed during the first few weeks. Use a drip acclimation process and dim the lights when you first introduce them. Provide several potential burrow spots from day one; this helps them settle in faster and reduces the urge to jump.

For a broader overview of bringing new fish home safely, see our step-by-step guide to quarantine and acclimation for saltwater fish.

Is the Blue Dot Jawfish Right for You?

The Blue Dot Jawfish is best suited to hobbyists who appreciate natural behavior and are willing to design their tank around a burrow-building fish. With a secure lid, deep mixed-grain sandbed, stable parameters, and careful tankmate selection, this species can thrive and become one of the most engaging residents in your aquarium. If you’re looking for a fish with big personality in a small package, Opistognathus rosenblatti is an excellent choice.

Sources

• Michael, S. W. (2001). Marine Fishes: 500+ Essential-To-Know Aquarium Species. Microcosm.
• Fenner, R. (2008). The Conscientious Marine Aquarist (2nd ed.). TFH Publications.
• Divers’ and public aquarium notes on Blue Dot Jawfish habitat and behavior (Monterey Canyon / Gulf of California field observations).