Bristletooth conger
Xenomystax congroides
Bristletooth congers have elongated bodies, a distinctive bristly texture along their jaws, and exhibit varying shades of brown and gray.
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About the Bristletooth conger
This is a deepwater conger eel from the western Atlantic that cruises continental slopes hundreds of meters down. It gets big and prefers cool water, so it is more of a public-aquarium fish than a home tank fish. If you ever saw one up close, the long, slender build and toothy grin are pretty wild.
Also known as
Quick Facts
Size
87.6 cm (34.5 inches)
Temperament
Semi-aggressive
Difficulty
Expert
Min Tank Size
500 gallons
Lifespan
Unknown - likely 10+ years
Origin
Western Atlantic (Florida and Gulf of Mexico to the mouth of the Amazon, including the Bahamas and West Indies)
Diet
Carnivore - fish, crustaceans, and cephalopods; will take meaty marine foods in captivity
Water Parameters
10-19°C
8-8.4
8-12 dGH
Need a heater for this species?
This species needs 10-19°C in a 500 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Deepwater fish - run a chiller and keep it cool and dim: 12-18 C (54-64 F), low ambient light, and lots of surface agitation for oxygen.
- Think very big tank with a long footprint (8 ft+, 300+ gallons) and a tight, locked lid with every gap and overflow covered - they will find any hole.
- Give it a soft layout to prevent snout damage: 4-6 inches of fine sand and wide PVC caves (3-4 inch diameter) buried and wedged so they feel snug.
- Kickstart feeding with live bait shrimp or small saltwater fish at dusk, then switch to tong-fed strips of squid, marine fish, and shrimp; feed 2-3x per week and vitamin-soak the food.
- Skip freshwater feeders and do not rely on smelt/silversides as a staple (thiaminase risk); variety keeps them eating and prevents deficiencies.
- Best kept solo; it will mow through crustaceans and any fish it can fit in its mouth, and triggerfish or puffers may harass or bite it.
- Heavy filtration and a big skimmer are your friends: keep ammonia and nitrite at 0, nitrate under 20 ppm, salinity 1.024-1.026, and pH 8.0-8.3 - they are messy eaters.
- Avoid copper-based meds on eels; quarantine in a chilled, dim tank and use short, well-aerated freshwater dips or praziquantel for flukes if needed. Watch for refusal to feed and face rubs; darken the tank sides, add more cover, and move it using a PVC tube, not a net. Breeding in home tanks is not happening.
Compatibility
Good Tankmates
- Mid to large tangs and rabbitfish that cruise the water column and are too deep-bodied to be a meal
- Robust wrasses like Halichoeres, Thalassoma, and big Coris types - fast daytime movers the eel ignores
- Squirrelfish and soldierfish that hang under ledges - size them up so they are not snack-sized
- Larger angelfish (Pomacanthus, Holacanthus) that hold their own but are not chronic pickers
- Bigger butterflyfish like Heniochus and large Chaetodon that stay midwater and mind their business
- Stout hawkfish like arc-eye or spotted hawk that perch boldly and are too large to swallow
Avoid
- Small, slim fish the eel can inhale after lights out - gobies, blennies, chromis, juvenile damsels, anthias
- Crustaceans like cleaner shrimp, ornamental shrimp, and most crabs - night-time snacks
- Triggers and nippy puffers that target tails and faces - they stress and injure eels
- Other eels or snake-like fish in tight rockwork - cave turf wars and bite marks
Where they come from
Bristletooth congers are deep Atlantic eels, mostly from the western side. Think continental slope, not reefs. They show up from the Carolinas and Bermuda down through the Caribbean into Brazil, usually way below recreational diving depths. Pitch-dark, cold, and quiet places. That background explains a lot of their aquarium quirks.
Setting up their tank
These are big, secretive eels that need space, low light, and cold water. If you cannot run a dependable chiller, skip this species. They are deepwater fish and run poorly at typical reef temps.
- Tank size: plan for a dedicated system. Juveniles can start in a 180 gal (6 ft), but adults really want 240-300+ gal with a long footprint. Bigger is kinder.
- Temperature: 12-18 C (54-64 F) holds well for deep-caught specimens. Keep it stable. Above low 20s C/70s F and they go downhill fast.
- Salinity: 1.025-1.026. pH 8.0-8.3. Ammonia and nitrite at 0, nitrate as low as you can keep it.
- Oxygen: high. Run strong gas exchange: oversized skimmer, vigorous surface agitation, and do not let the chiller strip too much O2.
- Lighting: very dim. I use a red LED strip at night for viewing.
- Aquascape: heavy rockwork or large PVC caves (4-6 inch diameter) anchored so nothing shifts. Fine sand is kinder on their skin and jaw than crushed coral.
- Flow: steady, not blasting. Enough to keep oxygen up and detritus moving, but leave calm lanes near the caves.
- Lid: absolutely escape-proof. Weight it, clip it, and seal cable gaps.
Chiller required. Do not attempt this species at tropical reef temps. Warm water and low oxygen are the fast track to losses.
Add the eel first and let it claim a proper cave. If it settles, everything else is easier.
What to feed them
They hunt by smell, not sight, and many arrive not recognizing aquarium food. Be patient and feed at dusk with tongs.
- Starter foods: live ghost shrimp, small live crabs, or gut-loaded mollies (salt-acclimated). Use these only to kick-start feeding.
- Transition foods: silversides, lancefish, squid strips, shrimp, pieces of marine fish. Scent with a drop of clam juice if they hesitate.
- Routine: 2-3 meals per week for settled fish. Offer modest portions; they regurgitate if you overdo it.
- Method: long feeding tongs, wiggle the piece right at the cave entrance. Keep the room dark and quiet.
If it will not take dead food, try turning off all pumps for 10 minutes and use a red light. The still water helps the scent hang in place.
How they behave and who they get along with
Mostly a cave-dweller that peeks out at night. Not aggressive for the sake of it, but anything it can swallow is food. They do quick ambush strikes and retreat.
- Best setup: species tank. Life is simpler for both you and the eel.
- Possible tankmates (advanced keepers only): large, cool-water fish that ignore eels and are too big to swallow. No nippers, no hyper tank bosses.
- Avoid: small fish, shrimp, crabs you care about, and other eels in normal-sized systems. Conger-on-conger scuffles happen in tight quarters.
- Activity: crepuscular to nocturnal. They get bolder once they trust the routine.
If it fits in the mouth, it is on the menu. Do not test boundaries with expensive tankmates.
Breeding tips
Realistically, none for home aquariums. Like other conger eels, they have a leptocephalus larval stage and spawn in the open ocean. There are no hobbyist reports of captive breeding, and public aquariums have not cracked it either.
Common problems to watch for
- Refusing food: very common early on. Keep it dark, offer at dusk, try live starters, and wean to dead foods slowly.
- Heat stress: gaping, frantic attempts to leave the tank, and rapid decline. Double-check the chiller and oxygen.
- Mouth and nose abrasions: they ram lids and rocks. Use sand, smooth PVC, and solid rockwork that does not shift.
- Escape attempts: any gap is a door. Weight the lid and block cable cutouts.
- Collection damage: deepwater fish sometimes arrive with barotrauma or internal issues. Expect a rough first month and keep stress low.
- Medication sensitivity: like other scaleless fish, they do poorly with copper. If you must treat, use alternative protocols and test carefully.
- Water quality swings: they are messy eaters. Oversize filtration, change socks often, vacuum the cave mouth area, and keep ammonia at absolute zero.
Quarantine in a dim, chilled tank with a snug PVC cave and lots of oxygen. Skip aggressive prophylactic meds. Observation and gentle husbandry go further with this eel.
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