Pullus viviparous brotula
Nielsenichthys pullus
Pullus viviparous brotula exhibits a slender, elongated body, with a mottled brown and green coloration, and prominent, long dorsal fins.
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About the Pullus viviparous brotula
This is a tiny little livebearing brotula from reefy coastal waters around Bali, Indonesia, topping out at only about 3.8 cm standard length. It is basically a secretive, bottom-hugging marine fish you would expect to live tucked into cracks and crevices, and its whole genus is just this one species.
Also known as
Quick Facts
Size
3.8 cm SL
Temperament
Peaceful
Difficulty
Expert
Min Tank Size
20 gallons
Lifespan
unknown
Origin
Indonesia (Bali, Nusa Penida area)
Diet
Carnivore/invertivore - likely small crustaceans and worms; offer tiny frozen foods
Water Parameters
24-28°C
8-8.4
8-12 dGH
Need a heater for this species?
This species needs 24-28°C in a 20 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a dim, cave-heavy tank with tight rockwork and rubble - they want cracks to wedge into, not open water. Lock down the lid and any overflow gaps; they can snake through stupid-small openings.
- Keep salinity stable around 1.025-1.026 and temp about 24-26 C (75-79 F); they hate swings more than they hate slightly-not-perfect numbers. Nitrate low and oxygen high with real flow, but make a few calm pockets near the caves.
- Feed like a nocturnal ambush fish: small meaty stuff after lights-out (mysis, chopped shrimp, enriched brine, tiny pieces of clam). If you only feed daytime, you'll think its starving while the cleaner crew steals everything.
- Target-feed with a pipette right to its cave entrance so it actually gets food and you dont end up nuking the tank with leftovers. If it starts spitting food, your pieces are too big or too hard - chop finer and rotate softer foods.
- Tankmates: quiet, non-bully fish that wont outcompete it at feeding (small gobies, blennies, passive wrasses if the tank is big). Avoid aggressive dottybacks, hawkfish, and anything that likes to pick at rock crevices.
- Treat it like a scaleless, delicate fish when it comes to meds - copper and harsh dips can wreck them fast. Quarantine with observation, gentle meds if needed, and dont blast them with freshwater dips unless you have no choice.
- Breeding is livebearing, so if you luck into a pair, dont expect obvious spawning like clownfish. If you suddenly see tiny threadlike fry in the rockwork, move them or the tank will eat them - they need clouds of tiny live foods (rotifers/copepod nauplii) right away.
Compatibility
Good Tankmates
- Peaceful gobies (neon gobies, clown gobies, watchman-type gobies) - same mellow vibe, they stick to their own little zones and usually ignore a brotula
- Small, chilled blennies (tailspot-type, bicolor-type if its not a jerk in your tank) - lots of perching and grazing, not much interest in picking on a secretive fish
- Cardinalfish (Banggai, pajama cardinals) - slow, peaceful midwater fish that do not hassle cave-dwellers and are fine with lower-key tankmates
- Firefish and dartfish - gentle and shy like the brotula, just make sure both have bolt-holes so nobody feels exposed
- Small fairy/flasher wrasses (the calmer ones) - active but typically not mean, and they mostly cruise the water column while the brotula stays tucked in
- Peaceful reef-safe basslets like a royal gramma - usually works if you have multiple caves and broken-up rockwork so the gramma cannot claim the whole bottom as its turf
Avoid
- Dottybacks (especially pseudochromis) - too territorial and nosy around rockwork, and they love to investigate the same caves a brotula wants to live in
- Aggressive damsels and mean clownfish pairs - constant chasing near the rock can keep a brotula pinned in its hidey-hole and not eating well
- Hawkfish - perch-and-pounce predators that will harass smaller, shy fish and sometimes go after anything they can fit in their mouth
- Big predators like groupers, lionfish, morays - if it can swallow a brotula or rip it out of a crevice, it eventually will
Where they come from
Pullus viviparous brotula (Nielsenichthys pullus) is one of those deep, cryptic reef fish that almost never shows up in the casual hobby. They come from marine habitats where light is low, structure is everything, and food drifts by in small, meaty bits.
That background explains pretty much all their quirks in captivity: they want caves, they hate chaos, and they do better when you feed like you're trying to satisfy a picky nocturnal predator.
If you are used to flashy reef fish that beg at the glass, this is the opposite vibe. You may only see it at dusk, at feeding time, or when the room lights are off.
Setting up their tank
Think "secure cave system" first, everything else second. I have had the best luck treating them like a secretive eel-ish fish that wants to wedge itself into a dark crevice and feel the rock around its body.
- Tank size: bigger is easier for stability, but footprint and rockwork matter more than gallons. Give it multiple tight hideouts, not just one big cave.
- Rockwork: lots of interlocking rock with narrow slots. PVC elbows hidden under rock also work and are easier to clean.
- Substrate: fine sand is fine, but not required if your rockwork provides the cover.
- Lighting: keep it moderate. If you run bright reef lighting, add shaded zones and overhangs so it can choose darkness.
- Flow: moderate, not blasting its favorite hole. Aim for good overall turnover without turning its cave into a wind tunnel.
- Filtration: heavy on biological filtration and export. These fish do best in tanks that handle meaty feeding without spiking nutrients.
Make at least 3-5 "good" hideouts before the fish goes in. If there is only one prime cave, it will glue itself there and defend it, and you will have a hard time managing tankmates.
Lock down your lid. Any brotula-like fish can surprise you with climbing or sudden dashes, especially on the first nights. Cover overflows, cable gaps, and weir teeth if they're large.
Acclimation is where people lose them. I do slow drip acclimation, lights off, and I do not try to "introduce" it with lots of activity in the room. Let it find a hole and settle. The first 1-2 weeks are all about getting it eating reliably.
What to feed them
They are small-predator eaters. If you offer flakes and hope for the best, you will be disappointed. Mine did best on a rotation of frozen meaty foods and the occasional live treat to kick-start a shy new arrival.
- Staples: mysis, chopped krill, chopped shrimp, chopped clam, squid strips cut small.
- Great additions: enriched brine (as a bridge food, not a long-term staple), fish eggs/roe, finely chopped seafood mixes.
- Live foods (use sparingly): live ghost shrimp or small live marine crustaceans can help a new fish recognize food.
- Feeding schedule: small meals more often beats one big dump. I like feeding near dusk and again after lights out if it's shy.
Use feeding tongs or a turkey baster and place food right at the cave entrance. Once it learns the routine, it will start poking out earlier.
These fish can starve slowly while "looking fine." Watch the belly line and body thickness behind the head. If it is getting pinched, change tactics fast (target feed, quieter tank, different foods).
How they behave and who they get along with
Expect a shy, cave-bound fish that becomes confident only after it knows the tank. They are not a community "open water" fish. Most of your interaction is going to be at feeding time, and honestly that's part of the charm.
Aggression is usually about real estate. If it has a cave it likes, it will hold it. If it does not have a cave, it will be stressed and may lash out at whatever is closest.
- Good tankmates: calm, non-bullying fish that won't wedge into the same holes (some gobies, calm wrasses, smaller peaceful species that stay in the water column).
- Avoid: aggressive rock-pickers and pushy feeders (many dottybacks, large damsels, big hawkfish), and anything that will harass it in its hole.
- Also avoid: tiny fish or shrimp that could fit in its mouth once it settles in. Even if it ignores them at first, that can change.
- Multiple brotulas: only attempt if you have a large tank with a lot of separated rock structure. In small setups, it often turns into a cave war.
They can look "inactive" but still be perfectly healthy. Judge by feeding response, body condition, and breathing, not by how often you see it cruising.
Breeding tips
They are livebearers (viviparous), which is wild in a marine fish. In home aquariums, breeding is possible in theory but not something most people stumble into casually. The bigger challenge is usually getting a compatible pair and keeping them settled long-term.
- Give them privacy: lots of caves and minimal interference. Spawning behavior is easy to disrupt with constant rearranging or loud, busy tankmates.
- Feed heavy but clean: meaty foods and consistent nutrition seem to matter, but you will need nutrient export to match.
- If you ever see tiny, fully formed young: move them or protect them immediately. Adults and tankmates may snack on them, and filtration intakes can grab them fast.
If you try to raise fry, plan for dedicated tiny-food culture (pods, enriched baby brine, etc.) and a safe grow-out system. "I'll figure it out later" usually ends with no survivors.
Common problems to watch for
Most issues with Nielsenichthys pullus come down to stress, shipping damage, and not getting them eating early. They are not forgiving fish, which is why I call them expert-only.
- Not eating: the big one. Causes are bright lighting, too much activity, strong flow on the cave, or competition at feeding time. Fix by dimming, target feeding, and choosing quieter tankmates.
- Rapid breathing and hiding constantly: often stress from harassment, poor oxygenation, or water quality swings. Check dissolved oxygen (surface agitation helps) and basics like ammonia and temperature stability.
- Skin/fin damage: can happen from rough rock, bad netting, or being chased into tight crevices. Smooth out sharp rock edges near favorite holes and use containers instead of nets when moving them.
- Parasites (especially on new arrivals): treat like any delicate marine fish - quarantine if you can, and avoid rushing harsh meds if the fish is already not eating.
- Jumping or overflow accidents: almost always a lid/overflow gap problem during the first nights.
Do not buy one unless you have a plan for getting it to feed in the first 48-72 hours. A shy, newly imported brotula that is outcompeted at meals can go downhill before you realize it.
If you nail the basics - dark hideouts, calm tankmates, and targeted meaty feeding - they can settle in and become a really cool "you only see it if you know where to look" fish. Just go in expecting a project, not a showpiece.
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