Southern Smiler

Where they come from

Southern Smilers (Opistognathus jacksoniensis) are jawfish from temperate Australia, and they act like it. Think sandy patches near reef and rubble zones where they can dig a burrow, sit at the entrance, and watch the world go by. If you give them the right bottom and a place to build, they settle in and become one of the most fun "pet" fish you can keep.

Setting up their tank

Build the tank around the burrow. If the substrate is wrong, the fish is stressed, hides, or just keeps trying to dig under rocks and creates collapses. With jawfish, the bottom is the whole game.

• Tank size: I would not do one in less than 30 gallons, and 40+ is more forgiving. More footprint beats more height.
• Substrate depth: 3-6 inches works well. Deeper is better if you have the space.
• Substrate mix: fine sand plus some mixed rubble (small shell bits, small gravel, tiny coral rubble). They want building materials, not just powdery sand.
• Rockwork: put rock on the glass or on supports, then add sand around it. Jawfish will dig and undermine anything sitting on sand.
• Flow: moderate. You want oxygen and clean water, but not a sandstorm at the burrow entrance.
• Filtration: solid skimming and stable parameters. They do not love swings.

Temperature is a big deal with this species since it is from cooler water than a typical tropical reef tank. If you run your tank warm (like 78-80F), you are stacking the odds against it long-term. A cooler system (mid 60s to low 70s F range) matches their natural comfort zone a lot better. That usually means planning the whole stocking list around temperate conditions and, for many hobbyists, using a chiller.

What to feed them

Southern Smilers are eager eaters once settled, but they are not built to chase food all over the tank like a wrasse. They like meaty bits delivered nearby, especially while they are still claiming a burrow.

• Staples: mysis shrimp, finely chopped prawn/shrimp, enriched brine shrimp, small marine pellets (once they recognize them), and other small frozen meaty blends.
• Enrichment: soak frozen foods in a vitamin/HUFA supplement a few times a week if you can.
• Frequency: small portions 1-2 times daily is better than dumping a big meal once.
• How to target feed: use a turkey baster or pipette and gently drop food right at the burrow entrance. After a week or two, many will come out and grab from the water column.

How they behave and who they get along with

Most of the day you will see a head poking out of a burrow, watching you like a tiny security guard. They rearrange their doorway constantly. If something spooks them, they reverse into the burrow so fast it looks like a magic trick.

They are generally peaceful, but they are serious about their real estate. One fish per tank is the easy route unless you have a big footprint and can provide multiple burrow zones with visual separation. Even then, be ready to intervene if one gets pushed out and starts wandering.

• Good tankmates: calm fish that are not sand bullies and do not hover right over the burrow (think mild-tempered temperate species, small peaceful fish, and non-predatory inverts).
• Avoid: aggressive damsels, dottybacks, hawkfish, big wrasses, triggers, and anything that sees a jawfish as a snack or keeps pestering the burrow.
• Bottom competition: other burrowers and sand-sifters can be trouble. Constant sand churners make it hard for jawfish to keep a stable home.

Breeding tips

Jawfish breeding is cool because the male mouthbroods the eggs. If you end up with a compatible pair and a peaceful setup, you may see the male holding and refusing food for a bit while he carries the clutch.

• Start with: a settled pair, lots of burrow material, and low stress. They do not breed well in a "busy" tank.
• Signs: the male looks like he is chewing or holding something, stays close to the burrow, and may eat less.
• If you want to raise larvae: plan ahead. Larval rearing is the hard part (live foods, separate system, and lots of patience). Most people enjoy the behavior and let the tank handle the rest.

Common problems to watch for

• Jumping: the number one cause of sudden loss. Cover the tank completely.
• Too-warm water: chronic stress, poor appetite, and shorter lifespan. Plan a temperate setup if you want long-term success.
• Burrow collapse: rocks placed on sand, not on the glass. They dig under it and it shifts.
• Starving in a community tank: outcompeted at feeding time. Target feed until it is bold.
• Refusing food after introduction: often stress. Dim the lights, reduce traffic, and offer small meaty foods near the burrow.
• Parasites from wild collection: quarantine if you can, and do not ignore rapid breathing, flashing, or heavy mucus.