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!
Latest Animal Stories
Martha - 2020-04-17
Our knife fish did it again... we now have 4 in the tank. We don’t have room for this many knife fish. Now I’m going to have to net one and sell it to the fish store that we purchased the original 2 from.

Martha - 2019-11-10
We just learned that we accidentally bred our ghost knife fish. We got 2 about 1.5 - 2 years ago with absolutely no clue of their genders. About a two months ago we got home late and happened to notice that both knife fish were out of hiding, so we sat to watch them for a bit since they are so cool and we don’t get to see them frequently. They began swimming together in what I can only describe as a dance. We joked that they were mating, but never expected it to be accurate. We never saw any eggs, we never saw any fry, but today during a water change we discover a new knife fish - about 2-3 inches compared to the original two being about 6-9 inches. Details of our tank: 150 gallons, 78 degrees F, we shoot for weekly water changes of 20% but often in ends up be closer to two weeks. We have a large variety of other inhabitants in the tank, so we feed frozen brine shrimp, frozen blood worms, tropical flake, and algae wafers. We increased the food amount over the past few weeks since many of the smaller fish have been disappearing and we assumed it was due to night hunting. I honestly have no other details since this was completely by chance. From what I have read of the knife fish, this little guy should have died at every single stage, but he made it so we have three of these beauties now!

Gina - 2012-05-10
I have bought 2 bgkf and I have a 125 gallon tank. Both fish have died within a day of me buying them. I have 2 red tips a black shark and a rainbow shark. My water always tests fine pH is 7.0. I am confused and disappointed. I don't know what's causing the fish to die. Any help would be nice.

Click For Replies (12)
  • Jeremy Roche - 2012-05-11
    Could be the place you got them from. How did you acclimate them to the tank? They stress very easy so a slow acclimation is best.
  • Anonymous - 2012-05-11
    I allowed the bag to float for 15 minutes and than released them into the tank. They were active and found a hiding place. Next morning they were fine and a couple hrs later they died.
  • lauren - 2012-07-19
    Try buying them from a different place.
  • Fred - 2012-09-01
    Maybe cause there was two of them, they couldn't really identify anything cause they were both sending electrical waves that kept intercepting the others.
  • peggy - 2012-10-13
    i had gotten my first black ghost knife from petsmart on sale for 8.60 somethin like that anyway he died two days later also bought other fish and put them all togather i noticed an outbreak of ick so i treated with ick- out he must have died from that i took him and the others to be replaced and got a big run around like they didnt want to exchange for another id wasnt takin no for the answer now two days ago once i brought new one home along with others i exchanged but did not put them in the same tank since im battling ick from the outbreak from the fish i brought home that also killed my few others i had in the tank a few months before i bought the black knife and others from petsmart anyway i put the newer fish in i exchanged in a qaurintene tank 20 gallon just untill the ich clears from my 30 when i put him and the other fish in the qaurintene tank i noticed white spots on them so i put ick out in right away and the next day spots seemed to be almost gone but i lost the ghost knife , i geuss ill be takin him back and exchanging him im sure with alot of disagreeing i did call next morning to petsmart in benton harbor, mi and told them about the ick and they probley have it the guy said he diddnt but i know they do but he told me to pick up some thing called ick-attack by kordon wich cost 11.00 so before i exchange themim makin sure the ick is gone but other then that can someone please e-mail me on what i can do better or whatnot so i can enjoy the black ghost knife for a long time my e-mail is [email protected] thanks and im sure ill get grief from petsmart takin back the ghost knife for the second time within 3 weeks but oh well its not my fault for the outbreak they will just have to replace him, so here is my story of my losses hopefuly no more after this woud be nice so i geuss im not the only one out here that has lost a ghost knife but maybe two wich i believe it the stores of there non knowledge of ick in there tanks that customers dont kow about or them for that matter, peggy
  • MsMonique - 2012-11-06
    I bought my first Black Ghost fish about a month ago from Petsmart and I fell in love, however about 2 weeks later I could not find it in the tank. I have a 150 gallon tank and I looked everywhere in the tank and cold not find it. No remains indicating he was dead. I just recently bought 2 more less than a week ago and they seem fine. You do have to watch the fish you get from Petsmart. I suggest not purchasing anytime from Thursday thru Tuesday as they get a new shipment in on Thursday and therefore you run the risk of disease and the fish being stressed out from the shipment. I experienced 2 bouts of ick from my fish there, before I realized it was best to have a quarantine tank set up for new fish and not to buy fish when they first get them in. I did however by my ghost fish 2 days later only because they don't keep them more than 2 days in stock due to the high demand. Thankfully my 2 have survived for 5 days today. Good luck!!
  • Breezy - 2013-03-16
    Ick is due to stress. All fish carry the ick virus, it's when they are stressed it comes out. It's like a common cold for us. Immune system is down bam we get sick. To blame it on pet stores is ridiculous. It could have been the stress from being transported to your tank,or the stress of being shipped to the store. you should be checking the fish out before you purchase it anyways, never rely on someone else even if they claim to be 'experts.' When medicating you should use half the dosage because they are a scaleless fish they cannot handle a full dose.
  • kye turnbull - 2013-04-04
    White spot is not carried by all fish! A parasite, ichthyophthirius multifilliis, it comes on plants, fish that have it, gravel or water! It's not in every fish!
  • kye turnbull - 2013-04-04
    Although you are right about the scaleless dosing.
  • k. - 2017-05-17
    That's the coolest thing I've heard in a long time!
    I can't believe that little guy lived in your filter!
    This story made my day. Thanks. Good luck with the breeding! Don't give up. .
  • Bijay B - 2018-07-08
    i had 4 black ghost .firstly i bought 2 ghosts and while im feeding the size of one earth worm exceeds its mouth size and next day morning one of them died due because stuck in day another one got white spot ich and during treating i think water temperature increased lot and it died i have only one which has white spot ich also ...i tried with with yellow medicine,methylene blue and tettra cyline also but no channge in white spot ..can someone help me ...
  • A guy - 2018-06-26
    BGK fish does not go well with sharks. They are semi agressive and they always fight. They are probably too stressed, seeing that there were sharks in the tank which caused them to die
Alvin Ong - 2018-08-06
Hey, I am getting a 85 gallon tank (largest tank I can find in Penang, Malaysia) to replace my 48 gallon tank, which is seriously small. Inside got 6 clown loach, 1 B.G. Knife fish (already 30cm, had been kept for 2.5 years), 2 bearded pleco and 5 cories. Can I add another small B.G. Knife fish? I am fascinated by the B.G. Knifefish.

Click For Replies (1)
  • violet - 2018-09-17
    it is not a good thing to do ;with my B.G Knife fish it was defensive and the new B.G Knife fish was gone by the next day
chris - 2012-05-26
i bought 2 BGK fish, both about 5 cm (2 inches) they look fine but I am not sure if this is normal. One during the day just lies next to a plant not moving at all. I always think it's dead so I knock on the tank to be sure. I think it's just sleeping or something since it's a nocturnal fish. At night it's very active it swims all over the place but the other BGK stays in a pipe I put in the tank all day an night just swimming in the same place unlike the other one. Are they ok? My tank is 9.25 gallons (35 litres)is that ok? and how long does it take for them to grow to 15 cm(6 inches)?

Click For Replies (3)
  • lauren - 2012-07-19
    They get BIG like 18 to 20 inches in captivity and need a large tank. They are not super active swimmers they need probably a 50 gallon or more.
  • Eryn - 2012-10-29
    10 gallons is not even close to big enough for one of these fish, much less two. They are small now, but they will grow quick (even quicker if they are fed a high protein diet). You need to upgrade to a 50 gallon (minimum), or find a new home for these fish, before they get stressed out and die.
  • k. - 2017-05-17
    They might not have enough room. They are semi aggressive too. Maybe one picks on the other. That could be why he stays in that pipe. You need at least 80gall. For one bgkf. Please get a larger tank or find them a better home. They are not just fish they're pets.
Anita Nyhus - 2010-10-20

I was just reading your information about the black ghost, and I would just like to give a small update -
We bred this fish in our tank a couple of years ago, truthfully, we got lucky and we were quite ecstatic to find we had managed. At the time we thought we were the first ever to have bred these fish, but it turned out a guy in Finland had done it before us :)

However, also a tank owner in Queensland, Australia has been able to keep two babies.

Our little guy was found behind the filtration map, as the egg had been sucked in – there he developed without any disturbance, and so was the only survivor.

The male of the original breeding pair died, and the female was given away to another black ghost owner, and we have not had them for a while.

Only weeks ago, we bought ten black ghosts, so hopefully we will manage again. We keep them in 520 liters tank, with sand on one side and gravel on the other. Many roots and rocks, no surface plants, and give them lots of food, preferably red mosquito larvae.
The filtration is very strong, and I reckon we were "lucky" when the egg was sucked in. It could develop undisturbed on the back side of the "back to nature" background, where the other fish never entered.

I am sure there are several others that can now report that they have bred them, but at least I can guarantee you that it has been done :)

Click For Replies (4)
  • julie - 2010-11-07
    We have a tank (75 gallon) and We had two ghost knife fish... who are very happy with their environment. And at the moment we have 9 offspring of different ages. Its getting to the point where we need to sell some!
  • tHyNOx - 2010-12-02
    Wow! How lucky you are.. how I wish I could do so too.
  • hanzo - 2013-02-08
    How did you manage to breed ghost knifes? We have one about 8inches long in a 5ft by 2ft community tank. They are my fav fish in the whole world and i would love to breed them =)
  • k. - 2017-05-17
    I just want to say that's the coolest thing I have heard in a long time! I can't believe that little guy lived in your filter! Lol.that made my day! Thank you 😉 good luck with the breeding. Keep trying! 8
Merida DunBroch - 2016-01-31
I just got a black ghost knife today. All it does is swim in and out of the log and try to eat my bottom feeder. When can I start training it?

Click For Replies (1)
  • k. - 2017-05-17
    My 1st bgk took a week before he was in my hand. When I put him in the tank it took about a week for him to come out of hiding. As soon as he did I started feeding him freeze dried blood worms above his head. Three days after I held a algae pellet between my fingers not he started nibbling away. After that I put the pellet in my hand not put my hand in the water he swam right in my hand. Not shy at all. Give it some time to get use to coming out during day feedings. Always make sure that your hands are super clean!!
Godfrey Sullano - 2016-04-06
Hello I just had a new BGK... I was wondering if what tankmates can i put in my aquarium ? My aquarium for now is about 50galloons since my BGK is not large enough

Click For Replies (1)
  • k. - 2017-05-17
    If you do get other tank mates, don't get anything smaller than the bgk. Plus that little bgk is going to grow up to 20". You might want to read up on tank sizes and the bgk. They are a bit aggressive and will eat other fish. I hope this helps.
Anonymous - 2016-11-01
ive had my black ghost for about a week now i got him second hand and i believe he may be about 3 years old he has just started laying on his side on the bottom but when i open the lid or something he jumps up and seems completley fine he is eating well and doesnt appear to have anything wrong with him any explanations?

Click For Replies (1)
  • k. - 2017-05-17
    I have a yoyo boteia that does the same thing. I bought him because I had a red ram snail problem.he never laid down until he reached his full size. I asked my local pet store owner about this n she said he's stuffed from snails. I believe this because I have only one or 2 rams left. So check into it. Also might be the maturity of the fish. I hope this helps. If you find out more on the laying down, please let me know.
Melvyn Williams - 2013-04-30
Thanks for your advice regarding my BGK. I believe I will leave well enough alone for the moment. I purchased 2-1' Angel Fish yesterday. When I admired my tank in the morning, they had both 'given up the ghost'. They were fine last night, I always have the water tested before I purchase anything and it was fine. They had not been eaten so I want to refrain from the BGK being the culprit, however, I have 2-2' black sharks, who have now recognized their aggressiveness. Could they have become the new vultures of my tank? And if that may be the case will this change the overall character of my community tank of assorted loaches? Your assistance is appreciated. One more thing, I have some feeders (6) who managed to survive and are now 5' and about 1/2' thick that nip at each other. They started out as 1' last May. How big will they get?! WHO EAT MY ANGELFISH!!!

Click For Replies (4)
  • Clarice Brough - 2013-05-01
    I bet the Black sharks are the culprits who got your angelfish. But on a positive note, if you are keeping a community loach tank, you should be fine... but Angelfish aren't going to do so well. On your feeder fish, I'm assuming you mean goldfish by the size you've described of 5'. They can get up to 14' on average though, so will get to be big fish. The tank will  need 20 gallons minimum for each of the goldfish, plus plenty of space for your Black Ghost Knife, so you may have to consider getting a huge tank - or maybe moving somebody! Good luck:)
  • Cristie Williams - 2016-12-21
    Yes the Black knife will eat your angel fish. Mine did! That means he is hungry. If he is fed well and not real aggressive he won't eat them if they are bigger. They will eat anything that is smaller
  • k. - 2017-05-17
    I have 3 sharks. 2 black with orange fins, and one albino. Sharks are aggressive. I'm betting they picked at your angels over night until they died. Then everyone else ate the rest of the carcass. I had to buy a 100gal. Tank to stop my sharks from battling each other. Lots of hiding spots. I hope this helps.
  • k. - 2017-05-17
    I have 3 sharks. 2 black with orange fins, and one albino. Sharks are aggressive. I'm betting they picked at your angels over night until they died. Then everyone else ate the rest of the carcass. I had to buy a 100gal. Tank to stop my sharks from battling each other. Lots of hiding spots. I hope this helps.