Longray fangjaw
Zaphotias pedaliotus
Longray fangjaw features a slender body with elongated, pale pink fins and distinctive large, fang-like teeth on its lower jaw.
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About the Longray fangjaw
This is a tiny deep-sea bristlemouth that lives way down in the midwater-dark and comes up and down the water column on a day-night cycle. Its little light organs (photophores) and even a slight nightly color shift are part of the whole "life in the deep" vibe - super cool, but absolutely not a home-aquarium fish.
Quick Facts
Size
7.5 cm SL
Temperament
Peaceful
Difficulty
Expert
Min Tank Size
0 gallons
Lifespan
unknown
Origin
Atlantic Ocean and Indian Ocean
Diet
Planktivore (zooplankton)
Water Parameters
7.7-16.7°C
8-8.4
7-12 dGH
Care Notes
- Plan on multiple small feedings the first couple weeks until it settles in; if it is losing weight, it usually means it is not finding food, not that it is 'picky'.
- Tankmates need to be calm and not food-competitive - avoid fast wrasses, aggressive dottybacks, and anything that will outcompete or harass it out of its hole.
- Also avoid tiny fish and shrimp you care about; if it can fit in the mouth, it is on the menu once the fangjaw gets comfortable.
- Watch for shipping damage and mouth injuries (they smash their jaws on glass when startled); keep the tank covered tight because stressed deepwater types can jump.
Compatibility
Avoid
- Big, boisterous wrasses (sixline can be a menace, plus larger Halichoeres). Too pushy, they steal food and stress shy fish hard.
- Hawkfish (flame hawk, longnose hawk). They sit and pounce and love to bully smaller, slower fish - not a great mix.
Where they come from
Longray fangjaws (Zaphotias pedaliotus) are deepwater marine fish. Think dim, cold-ish, high-pressure habitat where food shows up in pulses and everything is built around ambushing and making the most of a meal. In the hobby, that translates to: they do not handle bright reef-life chaos well, and they are not forgiving if your setup is "close enough."
This is an expert-only fish for a reason. The hard parts are acclimation, feeding, and keeping it calm and uninjured. Most losses happen in the first few weeks.
Setting up their tank
Give them a low-stress, dim tank with lots of structure. You want overhangs, caves, and shaded lanes where the fish can sit and watch. I would not put one in a bright, open aquascape and expect it to settle.
Tank size is less about swimming room and more about stability and giving it territory without constant traffic. Bigger water volume helps you keep parameters from swinging every time you feed heavier or do maintenance.
- Lighting: subdued. If you run a reef, keep this fish in a shaded zone or a separate system.
- Flow: moderate, not blasting. You want oxygenation without turning its favorite perch into a wind tunnel.
- Rockwork: tight caves and overhangs, but leave a few clear ambush perches with a view.
- Lid: secure. Startle responses happen, and deepwater fish can surprise you.
- Filtration: oversized and mature. Feeding meaty foods means nutrient load and fatty films add up fast.
I like using a dim "dusk" period on the lights and feeding during that window. They come out more readily and you avoid frantic mid-day feeding responses from other tankmates.
If you can keep temperature on the cooler side of typical tropical marine (without swinging day to day), it generally lines up better with how these deepwater types live. Stability matters more than chasing a specific number.
What to feed them
This fish is all about meaty foods. In practice, the biggest hurdle is getting it to recognize non-live food and then keeping it eating consistently. Once it is taking prepared items reliably, life gets a lot easier.
- Best starters: live or very fresh items that move (depending on what you can source responsibly).
- Transition foods: thawed mysis, chopped shrimp, enriched brine (as a bridge, not a staple), small pieces of marine fish flesh.
- Staples once settled: varied frozen meaty mix (mysis, krill pieces, chopped clam, prawn), plus occasional larger chunks if the fish can handle them safely.
I feed smaller portions more often at first. A new fangjaw that gets a huge meal and then refuses food for a week is a common pattern, and it can spiral. Short, frequent feeds also let you watch its aim and make sure it is actually swallowing, not spitting and giving up.
Use feeding tongs or a feeding stick. Wiggle the food near its perch and let it commit. Once it learns the routine, it will take thawed food much more confidently.
Avoid feeding hard, sharp, or oversized chunks. Fangjaws can damage their mouth or get food stuck if you push size too fast. If in doubt, chop smaller.
How they behave and who they get along with
They are ambush predators. Most of the time they sit still and look spooky, then they strike fast. Because of that, you pick tankmates based on two rules: nothing that can fit in its mouth, and nothing that will harass it into hiding and starving.
- Good tankmates: calm, mid-sized fish that mind their business and do not outcompete at every feeding.
- Bad tankmates: fast, aggressive feeders (many wrasses, dottybacks, big damsels), fin nippers, and anything tiny enough to be viewed as food.
- Also avoid: big bullies that pin it into a corner or steal every bite before it can line up a strike.
They can be surprisingly sensitive to constant "drive-by" activity. If you have a busy community tank, the fangjaw may never fully relax. A quieter predator-style setup or species-focused system tends to go better.
Do not trust them with ornamental shrimp or small gobies/blennies. If it fits, it is a snack eventually, even if they ignore it for weeks.
Breeding tips
Breeding this species in home aquaria is not something you see with any regularity. Deepwater fish often have seasonal cues, specific courtship triggers, and larval stages that are not forgiving. If you somehow end up with a pair, the best "breeding tip" I can offer is to focus on long-term stability, heavy varied feeding, and low stress, then document everything. Even getting consistent spawning behavior would be notable.
If you ever observe pairing, spawning, or eggs/larvae, take photos and notes and share them with experienced breeders. For rare deepwater species, good documentation is half the battle.
Common problems to watch for
Most issues come down to three things: stress, feeding failure, and injury. If you plan around those, you will avoid a lot of heartbreak.
- Refusing food after arrival: very common. Keep lights low, reduce competition, offer smaller moving foods, and do not constantly chase it around the tank with a net or tongs.
- Mouth damage: can happen from hitting rock during a strike, grabbing too-large food, or fighting. If you see swelling or it stops eating, slow down feeding and keep water extra clean.
- Weight loss while "eating": sometimes they strike but do not actually ingest much. Watch the belly and body profile over weeks, not just whether it lunges.
- Ammonia/nitrite spikes from heavy meaty feeding: easy to do in a newer system. Test more than you think you need to.
- Parasites after import: treatable, but these fish do not like rough handling. A calm, controlled quarantine beats panic-dosing in a display.
If it is hiding nonstop, start by changing the environment, not the fish. Add shade, add a better perch, reduce lighting, and give it a predictable feeding spot. They settle faster when they can claim one "safe" cave.
Do not buy one that is already thin, has a damaged jaw, or is breathing hard in the store. These fish rarely bounce back from a bad start.
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