Animal Stories - Black Ghost Knife Fish

Animal-World Information about: Black Ghost Knife Fish

The Black Ghost Knifefish is the most well known species of knife fish in the aquarium industry!
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Kimberly - 2010-11-21

I just purchased 3 black ghost knife fish and 2 silver tipped sharks for my 45 gallon aquarium. I purchased the fish at PetSmart and was told to add water conditioner to the tank. I did so following the exact directions on the bottle and acclimated my fish to the tank leaving them in the bag and putting the bags in the tank for approximately 40 minutes for the temps to adjust. About 30 minutes after I introduced them to the tank they started dying off. The temperature of the tank is 82-84 degrees Farenheit, and the pH level is 7.6 which according to this site is the appropriate level and temps for both kinds of fish. I now have one silver tip shark surviving. Could someone please tell me or give me any suggestions as to how or why these fish could have died so quickly? I think it may just have been the fish from PetSmart, but I've purchased other fish from there that have lasted years. There were no other fish in the tank when I introduced these new guys to the aquarium and the water was fresh with everything rinsed off in warm water. The filter had been running for over 12 hours to make sure everything was clean and ready for these new fish. I just don't understand so any help would be greatly appreciated!

Thank you,

Kim from Glen Burnie, MD

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  • Enrikus - 2010-12-21
    Water is too bad.
    *ph around 7 (6.7-7.3) is best.
    *make sure your tap water is hardness or softness. make medium water softness and hardness.
    *Degress is ok but better between 80-82
    *black ghost knife need 125 gallons up+
    *filters run 24hour. make sure ammonia and nitrite to 0. don't worry about nitrate between 1-2ppm is fine. water change can help low nitrate.
    *tap water have chlorine, add carbon in filters.

    Hope that helps you.
  • jessica - 2011-01-03
    I disagree with a lot of the people on fish set ups. I don't honestly believe the tank has to be over 100 gallons for a Knife fish. Your tank set up sounds almost perfect. I agree with the last comment though and that you should make so minor adjustments to temperature and pH levels. I think where you went wrong is: you shouldn't have bought so many fish to start out a new tank and you did it a little too early. It's probably best to wait 24 hours. My 30 gallon tank has been running empty for about a week now and I just put fish (guppies; because they are a hardy breed) in it today. I have done some research on the Black Knife fish because I really liked them when I saw one in the store. They do say that you should have a 50 gallon tank at least, but in reality any fish (as well as any reptile) will only grow as big as the tank they are in will allow them. As for the 'Clean and Ready' thing, there are a couple cycles the tank has to go through before the fish can be added. You did the right thing by putting in the water conditioner, but you should have waited a day or so after putting the treatment in for it to work properly. Next go round, (if you decide to go with Black Knife Fish again) I would recommend letting the tank run empty for a couple days. Put the treatment in it again if you are using new water. Test the pH levels and all other things you feel like you should test and wait another day or so to make sure it stays sustained. Then only put one or two fish in at a time. Also, I have read that you shouldn't try to feed them for the first 24 hours, because most wont even eat and usually it will stress them out in their environment. Hope this helps. Good luck next time.
Heather - 2010-12-09
Our BGK has been doing well since we got him in May, but now I'm getting worried. He recently came out of a growth spurt and now will barely eat and sleeps a lot. Of course, I've been panicking lately when I find him asleep because he sometimes doesn't respond or move when I touch him. (We hand feed ours and he loves to be petted.) I'm trying to figure out if this is normal behavior or if something could be wrong.

Chad - 2010-08-01
What are the odds the Black ghost knife will eat neon tetras?

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  • janine - 2010-08-18
    There seems to be 2 stories. Definitely will and they won't. Just be sure there aren't too many fish in the tank and perhaps feed your bkgf well. At night if possible. My ghost will chase fish when annoyed by them but doesn't go out of his way to fight. Nosy perhaps but not violent.
  • Becka - 2010-10-09
    From our experience, if the neons go into your BGKF's cave, pretty high... We got our bgkf (5ish in. at the time) at the same time as our neon tetras. We'd been told by the pet shop they'd be fine together.
    It wasn't until we saw tetras going into the cave but never back out we did some research and found bgkfs find neons pretty tasty...
    He had a go at our blue longfin fighter too, though the fighter lived to tell the tale (had one eye shocked out and some pretty bad fin damage though).

    It's at your own discretion really. If you DO decide to put both in the same tank just make sure you have a big enough school of tetras, a big enough tank and feed your bgkf at night. That's how we've kept our remaining tetras alive now :)

    All the best, they're fun fish really (minus blowing out eyeballs sometimes).
    I hope our novice mistakes can be of help :)
  • Heather - 2010-12-09
    The odds are very good if the BGK is hungry and the Neons are small. Our larger Neons don't seem to be on the menu though. Our BGK is approx 10" now and prefers bloodworms to anything else.
Mitchell Romanowski - 2008-08-18

I'm Mitchell Romanowski,

A couple of weeks ago I bought a black knife Goast Fish that was about 5 inches and cost about $30.

It's nocturnale\ and doesn't like light, so I made a cave for it to hide in.

When I feed the other fish, it doesn't touch the food because it doesn't want to go into the light to take the food.

A couple of days ago, I tried to hand feed it in the cave and it ate a whole cube of blood worms. The bits that it missed, the clown loaches and yoyo loaches ate.

I feed all fish including the ghost fish, brine shrimp, blood worms and high quality flake food to balance out their diets.

I've got about 15 plants, (small and big), in a large 4ft tank with lots of rock structures.

From Mitchell

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  • janine - 2010-08-18
    To mitchell romanowski. SOUNDS AWESOME
enrique - 2009-02-14
If anyone is really interested in breeding these fish email me at

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  • le - 2010-06-21
    I'm very interested I'm learning how to breed these fish any help on how to tell what sex they are would be a great start.
Lisa - 2010-03-31
I have a 110 gal tank with one bgk. I have had him for about 3 months. He was doing fine until tonight I noticed a white film or haze on his body. Is any thing wrong with him?

Calvin - 2010-02-08
To Kyle, I agree that too many people are too quick to tell others they are doing wrong. Your tank sounds fine to me. I had a black ghost knife over ten years ago. He lived for more than 12 years. He grew to about 16 or 17 inches. He was kept in a 55G aquarium. His tank mates at the time were nothing but guppies. And yes it was way beyond the 1 inch rule. As far as the 1 inch rule I too am old school. I knew about keeping bacteria in the filter, water changes, and Ph. 20 or so years ago that is all I cared about or knew about. I must have done something right to keep my ghost for more than twelve years. He also made an 18 hour drive from NC to IN. With that limited knowledge, "back in the day", I managed to keep Tiger Barbs with a breeding pair of angels, (lots of store credit). I still get upset when a fish dies as I am sure you do to. My four year old son is in charge of the flushing as I have taught him that "FISH DIE". I really enjoy the ones that read about the 1 inch rule and then explain that they have more than one BGK. I have read that you should not do this. Although, that is exactly my plan. I am hoping to gather info on the BGK and breed them. It is just a goal I have set. I have a room in the basement that is dedicated for this purpose. I have built aqua bridges to connect all my tanks together. Each tank is set up a little different. I am currently stationed in germany with the army. The water here has a Ph of about 7.8... higher than I prefer but it is what it is. I would love to find out more about your set up. If it is listed on this site give me time to find it as I am new here. Hope to hear from you and any other BGK keepers.

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  • MRJ - 2010-03-04
    Hey man I agree 100% with you, not all of the fish are the same. I recently bought a BGK and it is the most awesome of fish. I have read 100 different posts on how to care for a BGk and everyone says different things. =/
Sophie - 2010-02-12
Hi, I've just bought a 4inch knife fish, it's in my 190lt tank. He's with a clown loach, yoyo, pleco, cardinal tetras, harlaquins, and minnows. Was it a bad idear everyone seems fine at the momment. Please messege me sophie=price at symbol msn . com many thanks

Taryn - 2010-02-07
Hi, Well I have two black ghost knife fish at the moment. I must say they are awesome and very amusing to watch. My first BGK fish is about 9 inches, I bought him when he was just over 2 inches about 9 months ago. He lives in a 42 gallon tank with lots of plants and drift wood, eventually will be moving him to a 6ft tank, but for now he lives with a bunch of kuhli loaches, a pleco, a whiptail and a whole lot of cherry shrimp, all of which he leaves alone. He loves bloodworms and all other live/frozen food which I give as a treat, but he mainly eats sinking carnivore pellets. He will come out at any time during the day or night. My second BGK fish is currently living in my discus tank, she is only 3 inches and eats anything mainly carnivore sinking tablets and flake food. She is living with 3 breeding discus pairs and always leaves the eggs alone. She mainly comes out at night as she is only new. I've had her for maybe 2 months now, but she is getting more adventurous. She will also move to another tank in the future. In conclusion the Black ghost knife fish are awesome fish to keep. They are the first fish I have had. So as long as your willing to do the research I do not think experience plays a big roll in keeping them.

J - 2010-02-01
Kyle, Plecos and bottom feeders are included in that... they are bottom feeders and they count as fish. Yeah, it is over crowded with a freaking 10" pleco.