Keeping Multiple Black Ghost Knife Fish

Serpentine

Piranha
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May 17, 2018
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Common advice given is to never keep more than one black ghost knife fish in an aquarium. Supposedly they will fight, just as rainbow and red tail black sharks do.

A friend with far more experience than I stated that this is absolutely true... unless you keep a group and get them all as babies. Just as with the aforementioned sharks, you don't want to keep just 2 or even 3. A group of 4 or preferably more will diffuse aggression amongst the individuals and they will form a hierarchy.

I took his word for it and got a group of 6 baby BGKs. All are doing very well so far at the 1 week mark. If things go sour I can separate them. But each fish seems to have staked out its own small territory where it likes to hang out. They mostly stay out of each other's territories and all is well. I see them tootling about looking for food, usually 2 or 3 at a time. They show no aggression in common areas. And 2 of them have made friends and share their ghost house together.

The big thing seems to be making sure each fish has a place to call home and lots of things to break up lines of sight and provide cover. I have Lee's Ghost Houses all over the place, along with plants, rocks, hollow logs and driftwood. One of them prefers to hang out behind a filter stem.

They are tiny right now and are temporarily in a 90 gallon with juvenile Geophagus abalios and Mesonauta festivus but will be moving to a 600 gallon.

Has anyone else done this? What was your experience like? I trust my friend's advice and so far my experience has proven him right, but I'd be interested to hear from others who have done the same, especially long term.
 
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Bubbles_n_worms

Black Skirt Tetra
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Hey, I have kept 2 knife fish that ended in me having to rehome me My brown knifefish. I found over the many years I’ve had them we learn from our mistakes. The problem is in 5.6.7.8...years with that many u would need 150g for each! They torment each other with their sonar. The weak will die. Even at the Boston Aquarium they have only 1 BGKF in the exhibit. Some risks in this hobby are worth it, some are just not. I’ve learned...mine is my baby, I rehome fish to accommodate my BGK. I’m currently selling my XL clown loaches. Just too rowdy LOL ! But be assure my fish go to the best home not the highest bidder. I hope one day I can pass the years of hard work and love of my BGK to a gigantic TANK

7B91D97A-BD74-4264-A1F4-768727B92541.jpeg
 

Serpentine

Piranha
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May 17, 2018
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Hey, I have kept 2 knife fish that ended in me having to rehome me My brown knifefish. I found over the many years I’ve had them we learn from our mistakes. The problem is in 5.6.7.8...years with that many u would need 150g for each! They torment each other with their sonar. The weak will die. Even at the Boston Aquarium they have only 1 BGKF in the exhibit. Some risks in this hobby are worth it, some are just not. I’ve learned...mine is my baby, I rehome fish to accommodate my BGK. I’m currently selling my XL clown loaches. Just too rowdy LOL ! But be assure my fish go to the best home not the highest bidder. I hope one day I can pass the years of hard work and love of my BGK to a gigantic TANK

View attachment 1338599
Just out of curiosity, how much are you wanting for those XL clown loaches? Willing to ship?

Your BGK is lovely. I see why he's your baby.

Perhaps the problem was because there were only 2 and they weren't able to diffuse the aggression or establish a hierarchy? Or perhaps because they were different species? I was specifically warned that I could keep either 1 OR 4 or more blacks, but 2 would not work because they would rip on each other.

Regarding their sonar, apparently they use it to communicate with each other as well as to locate food. That was another thing I had worried about. I can see how it would be an issue with different species that don't speak the same "language" though. Bet that drove them bonkers.

If it goes badly like your experience I can separate them (I have a lot of tanks) but will only be able to keep 1 or 2 in big enough tanks long term. I would have to sell the other 4. I won't risk their lives. I love those guys.

So far the experiment with my group of 6 has gone very well. I got them as babies and all at the same time, which I was told was absolutely critical for success. There was some minor squabbling as they figured out whose territory was whose and who was in charge. Fortunately the worst damage we had was a slightly nipped pectoral fin before things settled down.

I made sure everyone had plenty of caves and hiding places, and each one has chosen a home. One lives behind a filter stem. One lives under a piece of driftwood. One lives in a fake rock cave. A few live in their Lee's Ghost Houses. 2 actually share a Ghost House together on occasion.

They do defend their territories but usually it's pretty mild. One will swim too close to another's house and the inhabitant will poke its head out like a moray eel and click its teeth as if to say, "Get off my lawn!" That's all it takes to get the other BGK to move along. We have one big guy with a lot of white on his tail who will actually chase the other fish for a couple of seconds before doing a 180 and returning to his cave. I think he's going to end up being the boss fish. When they are all out and about at feeding time or in common areas they are peaceful even when in close proximity to each other.

I noticed something last night after they had eaten that I couldn't explain. They were all swimming in a circle and it looked almost like a ritualized dance. No idea what it means, but it was beautiful to watch. Then they were done and each returned to its designated home.

They are getting along great with the juvie Geophagus abalios and Festivums. The Festivums are shy and I think a bit intimidated by the BGKs so I may move them if that doesn't change. The Geos watch them with curiosity sometimes but mostly ignore them. They like to hang out in the Ghost Houses that are uninhabited.
 

knobhill

Redtail Catfish
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You should be okay and hopefully you are successful in raising them up together. I had an awesome pair of adults that were 12"+ and they danced all night under the blue led lighting.

What are you feeding them?
 

Serpentine

Piranha
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May 17, 2018
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Maybe that dance is something that they do to socialize or to reinforce their hierarchy. Maybe it's just fun. :D Mine still do it.

No more bickering since everyone figured out whose territory was whose.

They eat pretty much everything I put into the tank. The seller told me that they were only eating live black worms but they greedily hoover up frozen and freeze-dried bloodworms, krill, plankton, cichlid flakes or pellets and shrimp pellets that I put in for the Festivums and eartheaters. They even nibble the pleco's algae wafers. They love live crickets and worms too. If it's edible they're on it. The one exception is veggies dropped in for the others. They want nothing to do with those.
 

Serpentine

Piranha
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Everybody's still doing well... growing, eating like pigs, getting along with each other and respecting their neighbors' territories.

Eventually the plan is to move them into a 600 - 700 gallon tank with a silver Arowana, a few Uarus, Rotkeil red shoulder severums, a royal plecostemus and a couple of Oscars.

They still do that oddly beautiful ritualized dance after they eat at night. They scatter if I disrupt them by getting too close so I just enjoy the show from across the room.

What amazing fish.
 

Serpentine

Piranha
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Still no aggression as they grow. They keep to their individual territories and come out at night to perform that ritualized dance together, swirling in endless, graceful circles.

I love these guys!
 

CrazyKoiCracker

Plecostomus
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Pictures? Update? I always thought multiple would mess with each other, interfering with each other electric field and causing sub dominant individuals to waste away. Very interested to see yours get along.
 
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Serpentine

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Still doing good, though I lost two of them along with some cichlids to human error. :( I was very sick and my husband did his best to help out by cleaning their tank for me. He didn't realize that you have to temp gun the water to make sure it matches the tank temperature. He just used "lukewarm" water and figured that was about right. Unfortunately lukewarm to a human is around 95F. He caught on to his mistake pretty quickly when he saw the fish in obvious distress and brought it back down as fast as he could to limit the damage, but our fish took it on the chin. I was surprised that the majority survived.

This is just a theory, but I think they actually use their individual frequencies like "voices" to communicate with one another, much like whales or dolphins use echolocation. No one seems to be weakened or debilitated by it.

I will try to get some decent photos. It's tricky to get really good ones because they are either in their ghost houses or in perpetual motion. They do come right out when food is offered so that's probably our best chance to catch them with tank lights on.
 

Kittiee Katt

Redtail Catfish
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Still doing good, though I lost two of them along with some cichlids to human error. :( I was very sick and my husband did his best to help out by cleaning their tank for me. He didn't realize that you have to temp gun the water to make sure it matches the tank temperature. He just used "lukewarm" water and figured that was about right. Unfortunately lukewarm to a human is around 95F. He caught on to his mistake pretty quickly when he saw the fish in obvious distress and brought it back down as fast as he could to limit the damage, but our fish took it on the chin. I was surprised that the majority survived.

This is just a theory, but I think they actually use their individual frequencies like "voices" to communicate with one another, much like whales or dolphins use echolocation. No one seems to be weakened or debilitated by it.

I will try to get some decent photos. It's tricky to get really good ones because they are either in their ghost houses or in perpetual motion. They do come right out when food is offered so that's probably our best chance to catch them with tank lights on.
Id love to see a video of their dance if you can get one! The vision in my head looks amazing, yet somehow I bet it looks even better than I'm imagining.. :hearts:

Ghost knives are my favorite knives.. Such elegant, graceful fish. My large one (10-11"ish) would have visitors mesmerized when she came out, as soon as she'd appear peoles eyes would be instantly diverted away from my big 12"+ geo straight to her.
 
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