Jurubida ghost knifefish
Apteronotus jurubidae
About the Jurubida ghost knifefish
Apteronotus jurubidae is a little Colombian ghost knifefish that cruises around using a weak electric field to "see" in the dark, and it can back up as easily as it goes forward. It is not something you will typically see in the aquarium trade, but it should behave a lot like other Apteronotus: shy by day, way more active at feeding time, and obsessed with having tight hiding spots.
Also known as
Quick Facts
Size
25.3 cm
Temperament
Semi-aggressive
Difficulty
Advanced
Min Tank Size
55 gallons
Lifespan
8-12 years
Origin
South America (Pacific slope Colombia - Jurubida River basin)
Diet
Carnivore/insectivore - small meaty foods (worms, insect larvae, small crustaceans), will take frozen foods and sometimes pellets once settled
Water Parameters
24-28°C
6-7.5
1-12 dGH
Need a heater for this species?
This species needs 24-28°C in a 55 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a long tank with lots of cover - PVC tubes, driftwood tangles, rock caves, and leaf litter. They hate bright light, so floaters or dim LEDs make them come out way more.
- Keep the water warm and steady: 78-84F, pH about 6.0-7.2, and soft to moderately soft (roughly 1-8 dGH). They crash fast from ammonia/nitrite and they do better with big, regular water changes than with chasing numbers.
- Run strong filtration with lots of oxygen and some flow, but leave calmer zones so it can hover and back into a hide. A tight lid matters - they can launch when spooked.
- Feed after lights-out: blackworms, earthworms, bloodworms, chopped shrimp, and quality carnivore pellets once its taking prepared food. Target feed with tongs near its hide so faster fish do not steal everything.
- Tankmates: peaceful midsize fish that will not nip or bully (bigger tetras, hatchetfish, calmer cichlids like severums if the tank is big). Avoid fin nippers, hyper feeders, and anything small enough to vanish overnight.
- Do not mix with other knifefish unless the tank is huge and you have multiple hides - they get territorial, and electric fish can stress each other out. If you try it anyway, add them at the same time and spread hides across the whole tank.
- Watch for stress from noisy tanks and voltage leaks - they are electric fish and get weird fast (hiding nonstop, refusing food, twitchy swimming). Also go easy on meds and salt; scale-less fish can react badly, so treat in a hospital tank when you can.
Compatibility
Good Tankmates
- Big, calm midwater schooling fish like larger tetras (Congo tetras, rummynose in a big group) - fast enough to not get bullied, not so tiny they look like food at lights-out
- Peaceful cichlids that mind their own business like severums or geophagus (eartheaters) - they share the space without constantly poking the knife
- Chill oddballs like pictus catfish or other larger, non-territorial catfish - they cruise around and generally ignore the knifefish
- Sturdy bottom dwellers like larger plecos (bristlenose or a medium panaque-type) - good match if you have enough hiding spots and wood so nobody fights over a cave
- Medium to large peaceful barbs like tinfoil barbs (big tank only) - active but usually not fin-focused, and they do not sit around inviting trouble
Avoid
- Other Apteronotus-type knifefish - only sometimes, and only in a big tank with lots of cover; they can get electric-territorial and one will stress the other out
- Anything nippy or pushy like tiger barbs, serpae tetras, or many rainbowfish that like to peck - they will harass the knife when it is resting and shred fins
- Tiny fish that fit in its mouth like neon tetras, guppy-sized livebearers, small rasboras - fine for a while until the knifefish starts hunting at night
- Big aggressive cichlids and tank bullies (oscars, green terrors, jack dempseys) - they will claim the caves and keep the knifefish pinned and stressed
Where they come from
Jurubida ghost knifefish (Apteronotus jurubidae) come from South America, in the Amazon basin region. Think warm, soft, tannin-stained water, lots of submerged wood, leaf litter, and dim light. They are built for cruising around in the shadows and feeling their way with their electric sense, not for bright show tanks.
Setting up their tank
If you are used to "community tank" rules, this one will make you slow down and plan. A. jurubidae is an advanced fish mostly because it hates sudden change and it is easy to stress with the wrong setup.
- Tank size: I would not start one in anything under 75 gallons, and 100+ gallons is a lot more comfortable long-term (they need room to glide, not just turn around).
- Filtration: strong bio filtration with gentle flow. You want clean water without blasting them around.
- Mature tank: they do best in a tank that has been running a while. Brand new setups feel like playing on hard mode.
- Hiding spots: piles of driftwood, long caves, and tight tubes. I like using PVC pipes hidden behind wood so you get a secure "burrow" that is easy to clean.
- Substrate: sand or smooth fine gravel. They spend time close to the bottom and you do not want torn skin.
- Lighting: dim. Floating plants, tannins from botanicals, or just reduced intensity helps them come out.
- Lid: tight. They can jump, especially if spooked at night.
Give them at least two real hides, not just one. They pick a home base, but having a second option cuts down on stress when you need to do maintenance or if a tankmate gets too interested.
Water-wise, aim for warm and on the soft side. Stability matters more than chasing a perfect number. I have had the best luck keeping them around 78-82F, low to moderate hardness, and a pH that stays steady (slightly acidic to neutral is the usual comfort zone). Big swings are what get you in trouble.
Do not mix them with "spiky" decor or sharp rock piles. They wedge themselves into places you would not expect, and they can scrape up their skin fast.
What to feed them
These are picky at first. Most new imports are shy and often come in a bit skinny, so getting food into them early is the whole game.
- Best starters: live blackworms, live or frozen bloodworms, and chopped earthworms. The smell gets their attention.
- Once settled: frozen shrimp, krill, mysis, chopped fish/seafood, quality sinking carnivore pellets (but do not expect pellets to be love at first sight).
- Feeding schedule: dusk and after lights out. If you feed in the middle of the day in a bright tank, you will wonder if they ever eat.
- Target feeding: use feeding tongs or a turkey baster to drop food near their hide. It makes a huge difference early on.
I like to feed a little, wait 5-10 minutes, then feed again. The first pass gets them comfortable, the second is when they really commit. Remove leftovers because meaty foods foul water fast.
If yours refuses everything, try live blackworms or freshly chopped earthworm. That has rescued more "not eating" ghost knives for me than anything else.
How they behave and who they get along with
They are mostly peaceful, but they are not a community fish in the casual sense. They hunt by electric sense and will absolutely eat anything that fits in their mouth. They also get touchy with other electric fish and other knifefish.
- Good tankmates: larger, calm fish that ignore them - think big peaceful characins, larger catfish that are not nippy, and mellow cichlids that are not territory-obsessed.
- Avoid: tiny tetras, guppies, small bottom fish, and anything shrimp-sized. Also avoid fin nippers (barbs, some tetras) and aggressive cichlids.
- Avoid: other knifefish and other Apteronotus unless you have a very large tank and a plan. Electric interference and territorial stress are real.
- Best vibe: low-competition tank. They do not like constantly being bumped off food.
A healthy jurubida ghost knife is often invisible during the day and then turns into a totally different fish at night. If you only watch your tank with full lights on, you will miss most of its behavior.
They are surprisingly personable once settled. Mine would learn the feeding routine and come out to meet the baster. But if you chase them around with a net or keep the tank bright and busy, they stay nervous and you will never see that side of them.
Breeding tips
Breeding Apteronotus jurubidae in home aquariums is uncommon. Most of what you see in the hobby is wild-caught, and even experienced keepers rarely report consistent spawning.
If you are determined to try, think in terms of giving them a big, quiet setup and letting them mature for a long time. A group in a very large tank, heavy cover, excellent water quality, and seasonal cues (slightly cooler period followed by warmer temps and more frequent water changes) are the usual "maybe" triggers people experiment with for knifefish in general. Just go in knowing you might do everything right and still never see eggs.
Trying to force a male-female pair in a smaller tank often backfires. Stress and aggression are more likely outcomes than breeding.
Common problems to watch for
Most issues with this species come from stress, poor acclimation, or water that is not as stable as you think it is.
- Not eating: very common on arrival. Fix the environment first (dim light, secure hide), then use stinkier live/frozen foods and feed at night.
- Skin damage: scrapes from decor, rough substrate, or frantic dashes into hardscape. Treat the cause, keep water very clean, and avoid harsh meds.
- Ich and other parasites: they can show up after shipping stress. Quarantine new fish and be cautious with medications.
- Medication sensitivity: knifefish can react badly to strong dosing, especially copper and some formalin-based treatments. Always research the specific medication and start gentle if you must treat.
- “Mysterious” declines: often from nitrate creep, old tank syndrome, or big parameter swings after a large water change.
Be careful with copper. If you keep snails or shrimp you probably avoid it anyway, but with knifefish I treat copper as a last resort and only with a test kit and a very controlled plan.
The best prevention is boring: a mature tank, steady maintenance, and not overfeeding messy foods. Once they settle in, they are tougher than people give them credit for, but they do not forgive chaos.
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