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FAQs on Black Ghost Knifefish, Apteronotus (Sternarchus) albifrons, Behavior

Ghost knife, BGK beh., sys. 3/3/08
I have had a 40 gallon freshwater aquarium for several years, and until recently the tank was home to a few Oscars who eventually out grew the tank and now reside in a friend's outdoor Koi pond. This past Christmas 12/07 we decided to re-establish the tank with two silver dollars and one incredibly elusive ghost knife. The tank contains your basic under gravel filter, bio wheel, plenty of colorful plastic plants and a long plastic tube, guess who lives in the tube. When I purchased the ghost knife from the pet store he was in a tank with several other ghost knifes and no real shelter, he was swimming around the tank, front wards, backwards and performing all sorts of tricks. Now that the ghost knife has a place to hide he never comes out of his tube. I love to tell friends about this mysterious looking fish, however when they ask to see him I can only reply with ummm sorry he's still hiding. Any suggestions on how my ghost knife can overcome his shyness?
<Apteronotus is only active in dark, shady aquaria. You need a soft substrate for digging, lots of rocks, and real or plastic plants that reach up to the surface of the aquarium and produce lots of shade. Use LOTS of floating plants (Indian Fern is ideal). What you do not want is brightly coloured gravel, bizarrely coloured plants, or bright light. Sounds and vibrations must be minimised, so don't put the tank near slamming doors or loud TV sets. Bob F just wrote a piece on setting up an African-themed aquarium, and the photo of the tank shown there is precisely what you need for Apteronotus, so have a read:
http://www.wetwebmedia.com/FWSubWebIndex/fwlvstksel.htm
Apteronotus live in major river systems and expect excellent water quality and lots of water movement. I'd be aiming for NOT LESS than 6 times the volume of the tank in turnover per hour. These are NOT easy fish to keep, and when kept poorly become shy, and often die.>
I also wanted to know if adding aquarium salt when doing water changes was harmful to the ghost knife?
<Yes.>
I know with other fish that I have had, I have added approximately 1 teaspoon of aquarium salt for every 10 gallons, however I recently read that ghost knifes are not particularly found of chemicals such as prime coat and aquarium salt.
<Indeed. The addition of Prime Coat and aquarium salt is unnecessary in a properly run aquarium. Instead focus on filtration and water quality. 50% weekly water changes and nitrates below 20 mg/l, and of course zero ammonia and nitrite, are what you are aiming for. Cheers, Neale.>

Freshwater fish electro-sense question
I recently bought an elephant fish. today my girlfriend surprised me with a black ghost knife. They are both about 3in and are in a 34 gallon tank with separate very good hiding spots. Will there 'electro-senses' clash?
<There have been some studies on these electromagnetic fields generated by these fish but not much in the popular aquarium literature. But I am sure that they are aware of each other.>
also how sensitive are they to salt?
<These fish come from clean warm acidic water and have become very sensitive to salt.-Chuck>
I use a little less then the recommended dose of aquarium salt(1tbsp per 5 gallon). tank also includes 6 glass cats and a blue lobster.
thanks for your time.
-Zac

Ghost Knife Turned cream
I have had my beautiful Ghost for over 8 months.  He's only about 5 inches long.  Recently I have noticed, that he has turned a very pale shade of light tan.
<be sure to check to see if his skin is turning the color, or does it appear to have a "dust" like coloration to his body.  It might be Oodinium (otherwise known as velvet). The visible symptom of this disease is a fine grey-gold to whitish 'dust' on the body of the fish. Fish will  usually show very rapid gill movement during this time. The disease is caused by a protozoan parasite, and may be triggered by exposure to ammonia and nitrite,  or excessive nitrate levels. That is if it appears to be something on the skin.  I've never heard of a ghost changing his color before.  Have you checked his water parameters lately?  Make sure that the ammonia levels aren't that high.  and be sure to keep up on the water changes.  If the fish isn't showing any signs of stress or sickness then I'm not sure what is the best course of action to take.  I wouldn't want to add a medicine to the water and stress it out if it's not needed.>
Nothing has changed in the tank-no new fish added, etc., so I don't know why he would be stressed.  He still bobs to the top to eat.  Have you ever heard of this?
<I haven't heard of this happening with a ghost knife, I would keep a close eye on him and make sure if you start to see any problems, or if the fish starts rubbing itself on objects in the tank to move it to another tank and start medicating it accordingly.>
Ren in Montana
<Good Luck with the fish. -Magnus>
Off-colored Ghost Knife and Oscars with Angels - 02/22/2004
Magnus...
<Sabrina, today, hope all is well>
Thought I would update you on my ghost who lost his color.
I put him in my 5gal guppies tank.  Thought that would be best - no one to intimidate him.  Of course, he loved the old car for his home, and as expected, the baby guppies all disappeared.  Had to make a decision of sacrifice to hopefully keep him alive.  I noticed a bit of black coming back (due to fresh "sea food" I'm sure...),
<And you'll surely have more baby guppies in the future, no worries.  Good that they have contributed to your ghost's well-being, a worthy cause, IMO.>
but he has outgrown the little tank,
<Heh, to be expected!>
so I moved him to the 38gal.  This tank consists of Parrots, Tiger Barbs, and a handful of misc.  The red tail shark is probably the most aggressive, but lives in harmony with the others usually.  Once in awhile he'll chase the barbs around.  So far the ghost has found an ornament to hide in and seems to being doing okay.
<IMO, all of these are too aggressive as tank mates - do keep an eye on him, watch closely for splits in his fins or any other signs of distress.>
Another question....I have a 60gal octagon with two Oscars, two tins,
<Hmm?  Ahh, tinfoil barbs, yes?>
two fire mouth cichlids and two angels and a silver dollar.  All is well with the combination at this point, but as the Oscars grow (one is about 6"), do you think the angels will be okay?
<Not at all, not in this size/shape tank - I would consider all tankmates grossly at risk of harassing/harming one another as they "grow up" - the Oscars will likely require a tank of their own, if they're getting on well, they've likely paired.  Removing them to their own space will give you some wiggle room for the rest, and the Tinfoils are the next biggest worry - topping out at about fourteen inches.  Fortunately, they are durable, and slow growers - I would remove them with the Oscars.  A tank that is big on surface area (er, not a hex/octagon/tall tank) will do best for the four.>
One angel is quite large, the other only about 2 1/2 inches.  I know there is not always a rule to go by, but do you
think I should move the angels?
<The Oscars and Tinfoils will need a larger tank in the long run.... not so much larger in gallonage as in usable space.>
FYI-my "herd" has gone down in numbers.  I have been very blessed to have had 6 adoptions in the past two weeks.
<Wonderful!!>
Down to 13 dogs-seems so quiet.
<Sounds like you're doing quite well.>
Thumbs up to your girlfriend for helping the shelters and rescues-wish she was here!
Have a wonderful day.  Ren
<You, too.  Wishing you well,  -Sabrina>

Black Ghost Knife habits
Good day,
I am writing to ask about the black ghost's behavior.
I notice that sometimes it lays on its side in the Mondo grass I have in my tank. Is it 'sleeping'? Or is it sick? I have never had a black ghost until my brother bought one for my birthday the other day. any answers would be appreciated.
< The black ghost is really a cool fish. Unfortunately it is nocturnal and is rarely seen during daylight hours. If you really want to see him out and about then you can turn off the aquarium light and feed the tank some black worms or live brine shrimp. Just use the room light to watch him. In bright light they will hide in logs or caves until dusk when they come out to feed. They get big, up to 18 inches but got to be up there as one of the strangest aquarium fish.-Chuck>
Thank you!
Eric

Training a black ghost knife fish 9/22/05
Dear Mr.  Fenner,
I have a black ghost knife fish that I have had for a month.  He is now about 7" long and very healthy.  He eats flakes in the morning and at  night, occasionally I give him some freeze-dried Tubifex worms.  What I  would like to know is how you teach them to eat out of your hand. He seems to be  a smart one he figured out the flakes were edible on his own.  If you know  how to do this I would really appreciate it.
Thanks for your  help,
MDM
<Try feeding small amounts of meatier foods, more frequently, particularly just with some light on outside the tank (not in... too bright). Takes time, patience. Bob Fenner>

FW algae and Apteronotus skin
Hi, In my 29 gallon tank there are re-brownish specs on everything. My water parameters are fine and I do weekly water changes and cleaning. what do you think it is?
<Almost undoubtedly algal colonies... take a read on WWM re>
Also I have a Black Ghost Knife for about 10 months now and since November he has shown a weird green/brown gel-like coating over him. I thought it was ick but wouldn't have died by now if that was the case. Do you know what it is and how to treat it?
thanks.
<This is probably the animals skin itself... and your good vision. The species is "quite slimy" in good health. Bob Fenner>

FW algae and Apteronotus skin, II
Bob,
thank you for the response I just wanted to add that my knifefish's slime is a little whitish-gray when the aquarium light is on, does that make a difference?
<Actually, yes... as stated, you have excellent vision, observation>
I mean when I go to the pet shop all the ones are pure jet black.
Jahner
<These are more stressed... Bob Fenner>

BGK suddenly shy 11/12/07
Hello Crew,
I've had a BGK for 8 months now.
He lives in a 55 gallon tank with 2 clown loaches, 3 discus, 2 rams, and a golden nugget Plec, with loads and loads of plants.
I do weekly water changes, and water conditions are almost perfect. ammonia 0, nitrite 0, nitrate trace. People always comment on how crystal clear my water looks.
He's been very healthy and happy, and growing slowly.
There are several hiding places for him but he has taken up home with the 2 clown loaches in a black tube.
<Predictably>
The three of them swim about looking for food during the day as well as when the lights go out. As soon as I drop food in, those three
are the first on the scene playing with each other and eating as fast as they can, its so cute to watch.
<Ditto>
But in the last 3 weeks or so, the BGK has stopped coming out. He just stays in the tube wiggling about.
At feeding time only the loaches come out. I'm very careful with over feeding so the food I put in is always all gone
within ten minutes. So I'm 99.9% sure the BGK hasn't eaten in 3 weeks!!
<Mmm, is eating something, assuredly... Perhaps you have other food... live worms and such, living in the gravel at this point>
Is it normal for these fish to suddenly change their behavior?
<Does happen>
Today, I fed my discus live bloodworm as a treat, one worm landed in front of the hiding tube and the BGK stuck his head out ate it and went back in.
My question is, how could a friendly full of life BGK suddenly become a scaredy cat? there has been no changes, no new tank mates, no change in feeding schedules.
My tank is always in view, and he never comes out, day or night.
Can there be a chance of illness with him? What can I do?
thanking you in advanced
Freddie
<If I had to guess... I'd say that the most likely possibility is that your Discus are getting larger, perhaps showing a bit of aggression toward this Apteronotid... Do try to spend a bit more time in front of the tank to observe... If two do pair off, there may be trouble for all the other fishes here. I might try some cultured black worms (tubificids) to urge this Knife's return to feeding. Bob Fenner>

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