Dusky Jawfish Care: Sand Depth, Burrows, Feeding and Lids

A new dusky jawfish spends its first day hiding. By the next morning there is a hole in the sand, a ring of shell bits around it, and a mottled brown face watching you from the entrance. Get the sand right and that burrow becomes the center of its life. Get it wrong and the fish lives in the rock, stressed, or ends up on the floor after a jump.

The dusky jawfish, Opistognathus whitehursti, is a western Atlantic fish. It lives from south Florida and the Bahamas down to northern South America, including the Gulf of Mexico and the Caribbean, in water from about 3 to 39 feet deep. It digs its burrows in rock and sand bottoms and along the eroding edges of seagrass beds, which is exactly the kind of bottom you find around the Keys. It is a peaceful, hardy fish with one hard requirement: a sand bed it can build in.

Quick facts

Scientific name	Opistognathus whitehursti (also spelled whitehurstii), described in 1927
Where it lives	Western Atlantic, south Florida and the Bahamas to northern South America, including the Gulf and the Caribbean
Depth	About 3 to 39 feet
Size	Up to about 5.5 inches. Usually sold at 1.5 to 3 inches.
Diet	Carnivore: mysis, brine shrimp, chopped seafood, pellets
Sand	At least 3 inches, mixed with rubble and shell. 4 to 6 inches where you want the burrow.
Tank size	30 gallons or more for one
Lid	Required. Jawfish jump.
Reef safe	Yes with corals. Very small shrimp are at risk.
Temperament	Peaceful with other fish, territorial with other jawfish
Breeding	Males carry the eggs in their mouths

The burrow is the whole fish

One detailed study of how this species digs is a 1974 Florida Atlantic University thesis by M. John Thompson, done on dusky jawfish. A few of its findings explain most of what a jawfish needs in a tank:

• The fish starts by wriggling its body to make a shallow pit. Once the pit is about a third of its body length deep, it switches to digging with its mouth, carrying sand out a mouthful at a time.
• A burrow takes five to six hours to finish. That is why you see a new hole the morning after you add the fish.
• The entrance tunnel is lined with coral rubble or shell pieces. Where jawfish dug depended more on having that lining material nearby than on the size of the sand grains.
• No burrow in the study was deeper than about 6 inches.
• Jawfish living near each other guard their territories hard against other jawfish and against smaller fish, with a color change during disputes.

Put those together and you have the setup: enough depth, enough rubble and shell to line the tunnel, and enough room that it is not staring at another jawfish all day.

Sand: how deep and what kind

Our listing asks for a sand bed of at least 3 inches with mixed rubble, shell and small rock. That is the floor, not the target. Build one area of the tank deeper, 4 to 6 inches, which covers the deepest burrow in the 1974 study, and let the fish choose its spot.

• A good mix is about three parts fine sand, with grains from 1/16 to 1/4 inch, to one part coarse pieces from 1/4 to 3/4 inch. Fine sand alone gives the tunnel nothing to hold it up. Coarse gravel alone is hard to dig.
• Scatter shell pieces and small rubble over the deep area. The fish will use them to line and repair the entrance.
• Set your rockwork on the bottom glass before you add sand. A jawfish can tunnel under a rock that sits on sand and drop it.
• Keep flow over the sand low to moderate so the burrow holds its shape.
• Do not put frags on the sand next to the burrow. The fish piles rubble around the entrance and will bury them.

Lids: why jawfish end up on the floor

Every source that covers jawfish says the same thing: they jump. A scared jawfish darts. With a burrow, it darts down. A new fish that has not built one yet has nowhere to go, which is why the first week is the riskiest.

A mesh lid has to cover the whole top, including the gaps around the overflow and the cord cutouts. A lid that covers most of the tank still leaves an exit. Turning on a room light a few minutes before the tank lights in the morning is a cheap extra precaution.

Feeding

Dusky jawfish are carnivores that pick food out of the water near the burrow entrance. Our listing calls for mysis, brine shrimp, finely chopped seafood and good pellets, two or three times a day. Ours are already eating prepared foods before they ship.

The trick is getting the food to the jawfish before faster fish take it. Thaw frozen food, suck it into a turkey baster, and release it in the water just above the burrow. The jawfish will dart up, grab it and drop back down.

A new jawfish may refuse food for a few days, and a week without eating is not unusual right after a move. If it is still refusing after that, try live brine shrimp near the burrow.

Tankmates

Tankmate	Fit	Why
Small peaceful fish: gobies, clownfish, firefish	Good	They leave the burrow alone and do not beat it to every bite.
Fast feeders, like a young wrasse	Some	No threat, but they eat first. Target-feed the jawfish.
Large wrasses, triggers, groupers, snappers	Poor	They hunt or bully small bottom fish.
Another dusky jawfish	Some	Only in a large tank with room for separate territories. Watch closely until the borders are settled.
A different jawfish species	Poor	Keep one jawfish species per tank.
Very small shrimp	Some	Jawfish eat small crustaceans. A tiny shrimp that walks past the burrow can become a meal. A Pederson cleaner shrimp that stays up in the rock is usually fine.
Corals	Good	It does not eat them. It may bury frags placed on the sand near its burrow.

Add the jawfish early, before bold fish claim the bottom of the tank. A jawfish that has its burrow built before the rest arrive settles better than one dropped into a tank of established bullies.

Tank size and where it fits

Plan on 30 gallons or more for one. Floor space matters more than gallons, because the jawfish lives on the sand. A long, shallow tank with a wide sand bed suits it better than a tall cube of the same volume.

It is one of the best fish for a Keys-style tank. It lives on the same sand and rubble bottoms as the rest of our local animals. See our Caribbean biotope reef tank guide for a full Florida Keys species list built around it.

Dusky vs yellowhead (pearly) jawfish

The yellowhead jawfish, Opistognathus aurifrons, often sold as the pearly jawfish, is the Caribbean jawfish most people picture: pale body, yellow head, hovering well above its burrow. The dusky is mottled brown and cream, grows larger, and stays closer to the sand. Our listing calls the dusky the hardier of the two, and quick to settle in.

Breeding and mouthbrooding

The female produces an egg mass held together by threads. The male takes the eggs into his mouth and carries them until they hatch. A brooding male holds a mouthful of eggs and may stop eating while he does. The larvae drift in open water, which is why jawfish are hard to raise at home.

Acclimation

Turn the tank lights off and float the sealed bag for 15 minutes to match temperature. Open it into a clean container and drip tank water in slowly for 30 to 45 minutes. Make sure the lid is on before the fish goes in. Net it into the tank near the sand bed and throw the bag water away. Expect it to hide for the rest of the day, and offer food the next day.

FAQ

The Underwater Gardener is a reef aquarium store in Key West, Florida. Our dusky jawfish are collected by our team in the Florida Keys. Livestock ships UPS Next Day Air on Tuesdays and Wednesdays.