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FAQs on Knifefish Systems

Related Articles: Knifefishes, GymnarchusBlack Ghost Knife, Electrogenic Fishes,

Related FAQs: BGK Systems, Knifefishes 1, Knifefishes 2, Knifefish Identification, Knifefish Behavior, Knifefish Compatibility, Knifefish Selection, Knifefish Feeding, Knifefish Disease, Knifefish Reproduction, Electrogenic Fishes,


Brown knife fish... Sys., fdg.,    12/31/09
Hey, I recently (2 days ago) got a brown knife fish,
<Is this Apteronotus leptorhynchus or Xenomystus nigri?>
and it hides in its clear tube all day AND night.
<Both these species are nocturnal, and unless the aquarium is precisely right for the species, they *will* hide away and eventually die from starvation. To recap, Apteronotus leptorhynchus needs moderately warm (25 C) water with a very strong water current and lots of oxygen. Water chemistry should be soft to moderately hard, slightly acidic to neutral (pH 6.5-7, 5-10 degrees dH). Xenomystus nigri needs similar conditions in terms of warmth and water chemistry, but isn't so fussy about water current. Both will be quickly stressed, even killed, by exposure to copper and formalin-based medications.>
I have dropped two cubes of blood worms in the tank, but I don't think its eating them and I'm pretty sure they are making a mess!
<May well be. Do remember neither species competes with catfish, cichlids, etc at feeding time. Apteronotus leptorhynchus in particular should be quarantined first, or at least kept with fish that offer no competition at all (i.e., just small midwater swimmers). Xenomystus is a little more adaptable, but won't feed if it feels threatened or bullied. Neither species is a community fish in the general sense, though careful fishkeepers can keep them with appropriate tankmates.>
Is there a more convenient way to feed frozen blood worms without them dirtying everything because once it breaks apart I can siphon all the worms out... I am going to try buying live worms... If I drop a bunch of live worms in.. Will he hunt them or something?
<These fish are greedy for live and wet-frozen foods including bloodworms, earthworms, brine shrimp, krill, etc. But they won't eat dried or freeze-dried foods, and they won't compete for food. Most critically of all, if conditions are inappropriate, they simply won't feed. Apteronotus spp. are notoriously sensitive fish, and among the first fish to die when conditions aren't right. Cheers, Neale.>
Re: Brown knife fish
Thanks so much!!
<You're welcome. Cheers, Neale.>
Re: Brown knife fish
It is a pteronotus leptorhynchus ..
<Apteronotus leptorhynchus is a lovely fish, a bit smaller than Apteronotus albifrons, but otherwise identical in terms of care.>
dude at pet store said it would be easy to keep..
<"Dude" was obviously making a sale. These fish are extremely difficult to keep. Wild fish live upwards of 15 years, but the vast majority of casual fishkeepers manage less than a year.>
I have a well planted tank (30gallons) with two coconut caves and a clear tube.
<He will need a much bigger tank eventually; I'd be saying a 55 gallon within a year or two. The size of the fish is rather less important here than its need for clean, oxygen rich water; these fish simply don't tolerate stagnant water conditions. They live in and around rapids and waterfalls, and expect not-too-warm, well aerated water.>
water conditions are fine...
<Define "fine".>
Should I not feed him for a couple days then try with live food?
<The problem with electric fish is they tend to need numerous small meals every day to be healthy. Presumably their energy demands are rather high.
In any case, starving these fish does little good, much harm.>
How long do you think it will take for it to accommodate?
<Kept on its own, should settle in within a week. Kept in a mixed community of poorly chosen tankmates, may never settled down at all.>
thanks again
<Cheers, Neale.>
Re: Brown knife fish
Okay well thanks for all the info.... The fish is swimming around now when the lights are off.. So I guess il feed it when its dark..
<Initially, this is probably best. Add modest amounts, and remove any nocturnal species (catfish, loaches) that would compete with your Knifefish.>
What's the easiest thing to feed them? worms? or crickets?
<Earthworms of appropriate size are very popular, as are live or wet-frozen insect larvae (bloodworms, mosquito larvae, glassworms, etc.). Cheers, Neale.>

New to Knives 8/2/04 I'm new on the knife fish thing so you might need to help me. I don't have any current problems but, I want to know if three glass Knifefish  in a 55 gallon tank is ok. < These fish have weak electronic organs and when they are kept together they seem to always be bickering amongst themselves. They don't do any real harm to each other so if you have plenty of areas to hide then they should get along fine. Males grow about 18" and females 11". A fish manual says 1" per gallon that would be 54" with three MALES. Here's the question. How do you tell male from female when they are the same size. < The books all say that the males get to be the larger fish. They are somewhat transparent so look for differences in the body itself. You may not see any until they get close to adult.-Chuck> They are about 4".((I have other fish in there already.))  Please Help If Possible. Thanks.

BGK in a 10g Tank!  2/3/07 Aloha, <Hello to you, Pufferpunk here.> I have 1 Black Ghost Knife, 3 small barbs, 2 small flying foxes and 2 small Kuhli loaches in a 10 gallon tank. <Oops!!!> I also have 3 small banana plants, 3 stalks of purple lilicina and 3 stalks of water sprite.  A friend got the BGK for me about 3 days ago on a whim. <Pets make terrible gifts!> I have no idea how to care for him, besides what I've found on your site.  Are the plants and other tank mates ok for him? I put some feeder shrimp in there and yesterday I put a frozen bloodworm cube in for him. The barbs devoured it (with a little help from the shrimp) but he didn't touch it. I realized about half way through the cube and realized I had the light on, so I turned all the lights off but he still didn't eat. I haven't seen him eat once in the last 3 days so I'm getting kind of worried. What kind of things should I be looking for as far as keeping him healthy? <This fish grows to 18" & will require a 90g tank.   Even as a juvenile,  10g just isn't appropriate.  The only thing you can do for this fish is find it a much bigger tank to live in.  They prefer live worms.  Please scold your friend!  ~PP> Sincerely, Jay

BGK in Small Tank  1/25/07 Hello Bob Fenner, <Pufferpunk here with you tonight Harry, I hope I'll do!> I have been doing some searches since a recent incident here in my fish tank a few days ago.  You seem to be a valuable resource on the topic.  I have a 25 gal. tank with 1 black ghost knife (8" or 9") and 3 barbs (not sure of type but long with brownish color and red tails). <That tank is way too small for a 9" fish. The BGK can grow 18+" & requires a 90g tank, minimum.  > Everything was fine until I came down to my basement office on Saturday and found the barbs white (lost color) and 2 of them on the gravel gasping.  I tested the water: pH, ammonia and nitrites all good.   <What does "good" mean?  Always post exact results when asking about your tank.> While testing I realized the water was cold and saw that the heater had cracked and was no longer functioning.  The tank went from 86+ degrees to 60 something (house thermostat set to 65 at night.   <Brrrrrrrr...> I installed a new heater, filled remaining tank room with warm water and gave StressZyme.   <Shouldn't raise the temp too quickly.  Can do more harm than good.> The barbs regained color almost immediately but the 2 on the ground died soon after.  The last barb seemed okay until I found him devoid of color (white) and laying on the bottom... somewhat bloated, later that night.  The whole time the knife had seemed to be okay until I checked on him Monday morning and he didn't look too good and hadn't eaten food from Sunday night. <Can you blame him?> Since then he has been spending most of the time laying on the ground or half in and out of the plastic tree stump he normally hides in during the day. The last thing I notice is that his front fins (at least the one that faces down at the time as he lays on his side) seems to hang down/loose.  I have had this fish for over three years and would hate to loose him.  Is he dying of thermal shock from the broken heater?  Should I be testing for other possible issues and how might I go about doing that? <Test for nitrates also (should be <20).  I'd do 25% water changes for the next few days.  I'd also start shopping for a much larger tank, so this fish doesn't stunt in the 25g tank.  It can grow extremely large in the right environment.  ~PP> Thank you very much, Harry

Black Ghost Knife in a 55g tank?  1/5/07 Hi, <Hi Iain, Pufferpunk here> My name is Iain and I am thinking about getting a Black Ghost Knife but I have been told they are hard to look after -is this true? - And if yes how do you look after them? <I think the biggest problem keeping these odd fish is feeding them.  Most will only eat live worms.  Mine hides, unless I am feeding & then it darts out of it's cave, eats & goes back into hiding.> Before I get my Black Ghost Knife I would like to know would it be ok in a tank (48x18x12) with plants, rocks and a decorative barrel? <I would say minimum--a 90g tank for these large-growing fish.> Also will it be ok with theses fish listed:- 1- 3x Silver Sharks      3-4 inches 2- 2x Plecos               3-4 inches 3- 1x Albino Shark       2-3 inches 4- 4x Silver Mollies       1-2 inches 5- 10x Zebra Danios     1-1.5 inches 6- 10x Penguin Tetras  0.5-1.5 inches 7- 10x Black Neons     0.5-1 inches Thank You for taking your time to read this Question <I think your tank is stocked quite well as it is.  The BGK has also been known to eat small fish.  Watch the adult sizes of those Plecos (if common Plecos, 18") & "silver sharks" (not quite sure what species those are--Bala sharks?  Also grow quite large, 14").  Great job for someone of your age!  ~PP> From, Iain MacPherson - aged 13 Re: No to BGK, FW Oddball fish?  1/5/07 Hi, <Hi again> Thanks for the information - so are you saying I should stay away from BGK- if yes, can you recommend any other oddball fish? <There are other smaller knife fish, like the brown knife & glass knife.  You will need a consistent live supply of worms for them though.  As far as other oddballs--I like the African butterfly but you must be sure to cover all of the tank at all times or they will jump. Same for the rope eel--another cool oddball.  Your best bet would be look through the WWM website & do some research on different species you may like.  ~PP> Thanks for taking your time to read my question. Iain MacPherson, aged 13 Black Ghost Knife--Tank Size?   12/31/06 Hi, <Hi, Pufferpunk here> I am considering purchasing a 36 gallon bowfront tank, which I believe measures 30x15x21. I have read that the African Knife can grow up to 12 inches but many never exceed 8 inches, is this true? <Mine is around 12" now.  There should be no reason a fish in captivity, if fed & housed properly, wouldn't exceed the size it can grow in the wild.> I am very interested in the African Knife and would like to know if the 36 gallon tank is large enough to accommodate a fully grown African Knife. I have read about compatible fish but am willing to keep the number of other fish in the take to as small a number as necessary. What do you think? <Definitely too small a tank.  They belong in at least a 90g.  ~PP>   Thank you for your time

Brown Knifefish, wrong env., tankmates  - 02/27/06 Hello!  I have a quick question regarding my brown ghost Knifefish.  Some background, I have a 29gal tank with a Eclipse 3 hood/filter;  20-25% water changes weekly, with tank salt added each time as well as conditioners. <Don't like salt> (The filter is changed every 3-4weeks);  Livestock:  Bala shark (approx 3yr old, 7in), <Too small a tank for> albino cat (about 4-5in); a blue white striped cat (about 3in); 4 ghost catfish (about 3in each); 1 Pleco (unsure the type-about 2 in); 1 pearl Gourami (3-4in); and the newest arrival (2mo.) a 4 in brown ghost knife- Charlie Brown; Ok, here's the problem.  I have provided plenty of cover for the BGK with (silk) plants and a 6in clear glass hurricane piece for cover/protection (which is completely ignored by him!) as well as a castle figure.  My question is regarding his health and behavior.  Charlie Brown (and the crew) is fed a mix of frz. blood worms or community mix (of krill, shrimp, etc) 1x/day, although I do not actually witness him eating very much at all. He spends most of the day (vertical) in the light  b/w the bubble wall and driftwood that is situated along the back. He has recently developed red spots in the gill area, and has lost some coloration. Can you please tell me if he is ill and is his behavior normal? <Is ill... poor tankmate choices (can't compete), likes different water than much of what you list... and the salt...>   And what, if anything, would need to be done?  Thanks! Rachel S. <Place this animal in an appropriate environment. Read re this per species on WWM, fishbase.org. Bob Fenner>

Clown Knife Fish   2/9/06 Hello, <Hi there> I am a recent aquarium addict (1 year) and need some information / help.  I have 3 aquariums (started with 2 beta bowls for decoration that never made it home before I rationalized purchasing an aquarium), one 30 gal (filtration - penguin 125) and a 55 gal (filtration - penguin 350).  The very BEST purchase I've ever made!!!!!  In my 55 I have a 7" clown knife, one Plecostomus, two 4" tinfoil barbs, two 2 1/2" albino tinfoil barbs and 4 giant Danios (did have four 1 1/2" but two of them weren't fast enough to duck the knife so I replaced them with two 3" ones) . <These will also be inhaled...> I plan to eventually get a 125 gal for all in the 55 gal, is this enough? <Not for the knife eventually> I plan to put filtration rated for 175, what do you recommend? <That you read WWM> Also, I started out feeding my knife pellets that it appears to not be eating - partly because of the greedy 6" Pacu (purchased in error due to bad information from LFS)   I got rid of before adding the barbs and Danios.  So I for obvious reasons (disease / filtration) reluctantly started feeding him 12 Rosies every 3-4 days and some ghost shrimp which he of course happily devours.  He recently ate all 12 Rosies in about 2 hours, should I be concerned? <Re what? Going broke? Disease? Behavior modification?> He has no problems with his tankmates as he comes out of hiding from time to time throughout the day (unlike with the Pacu) but still ignores the pellets.   How if at all possible can I get him to eat the shrimp pellets without starving him to death lacking live food? <Not likely to eat pellets...> Also, during the pellet spell he developed a 1/4" white stripe or spot which disappeared when he started eating live Rosies.  Might that have been stress related because he was waiting for a real meal? <Yes, good way of putting this.> I'm sure part of it was the skittish and supper fast Pacu, <Heeee!> but it started going away while the Pacu was there and I fed live food.  Although the tinfoil barbs are fast as well, they don't seem to bother him nearly as much because he comes out a lot more during the day. He looks to be in perfect condition on his new diet.  My other question is once I get the 125 gal, what more colorful tankmates do you recommend for my clown knife? <... perhaps some easier-going Neotropical cichlids like Juraparoids... or large/r minnow sharks that hail from the same part of the world as the knife...> Also, my 30 gal....heh, heh...thought I was finished eh....*grin*?  I have 4 tiger barbs, 3 albino tiger barbs, 2 albino rainbow sharks and a Plecostomus.  My only concern is the sharks seem to fight from time to time. <Very common> Well really the bigger one (3 1/2") chases the smaller one (2 1/2").  Will putting all fish from the 30 into the 55 once I upgrade to the 125 help this problem with the sharks?   <Likely will help> The Plec will be put in the 125 once it gets too big.  What other algae eaters do you suggest for the tiger barb / rainbow shark tank, because I only want 2 Plecos in the 125 and I know they get too big for the 30 and 55? <See WWM...> Or will a common Pleco be ok in a 55 gal?  My third tank....ok...ok...I'm wrapping it up.  I kept an iguana in a 55 gal aquarium that I want to use for fish.  Is it safe if it's cleaned and rinsed well?   <Should be, yes> Yes....definitely an addict...how did I go from Betta bowls to wanting 125 gal setups?  Are there any support groups out there? <Yep... Aquarium Clubs! And the Nets specialized BBs! Enjoy and keep sharing. Bob Fenner>

Brown Knifefish/African Knifefish ... comp., systems   2/3/06 We just recently purchased a brown Knifefish from the local PetSmart.  It is about 5 inches long and seemed to be doing fine.. at first.  After 2 weeks he has developed a coating in his skin, looks like dead skin or dust. <Bad...> We are very concerned and I read on your website about the parasitic disease that can be caused by ammonia and nitrate levels. <Yes... or just "unsuitable water quality" in general. Touchy fishes (S. American) knives... that like very stable, "clean", soft, acidic water of high temperature... and live foods, no rambunctious tankmates, subdued lighting... Wish the mass-merchandisers like PetSmart would leave off with such touchy animals> That sounded like what he has.  So, my question is- will fixing the ammonia levels and nitrate levels, doing a 30% water change with conditioner and vacuuming the gravel, fix the problem? <Possibly... hard to be very confident here... as if these fishes "go too far" they are very quickly lost... if assured as to real/root problems... or not, I might go with the addition of a Furan compound (Nitrofuranace) as well>   The fish is in a 55 gallon tank with lots of hiding places and the other fish leave it alone.   Thanks for your help!   Casey <Mmm, not really a "community fish" per se... I do hope yours recovers. Bob Fenner>

Black Ghost Knifefish, Quarantine - 10/17/2005 Greetings and salutations! I would like some advice on caring for a Black Ghost Knife. I brought home a healthy specimen at around noon, and put him in a 10 gallon quarantine. <Ah, good. Quarantine is essential with new stock.> He was a beautiful deep black with off-white markings, roughly 4 inches. It's now 2 AM and the entire front part of his body has faded to a silvery color. <Go to sleep! Actually, he could just be fading to more nocturnal colors.... though I cannot recall having seen them change to lighter colors at night - but many fish do.> It's as if his black is fading completely away! My QT water parameters: Nitrite/Ammonia-0ppm, Nitrate-10ppm, temp-78F, slightly hard water, pH 7.2. <What pH was he in at the store? He could be suffering from a bit of a shock from change in pH and hardness.... They hail from waters of low-ish pH and low-ish hardness, so this may be part of the issue. At this point, however, I would not change what you have - a steady pH is FAR more essential than a "perfect" pH.> The tank is bare but for 2 PVC pipes. <Large enough for him to enter and hide in?> The tank is in a private room, and the light is off. The fish is swimming "normally" (like an excitable drunk). Fed some frozen brine shrimp earlier, but he seemed to be spitting them out. <He may not eat for a day or so.... but likely you will need to start him on live foods. I could be mistaken, but I believe these animals are only wild-caught and not at all bred in captivity.> I read that these fish are very sensitive and their rich black color may fade due to stress, but I was wondering how common it is for this fish to fade so drastically in this short period of time!!! <Mm, 14 hours isn't really a short period of time.... a fish turning pale at night can do so in minutes. 14 hours is more than plenty of time for the fish to get stressed, as well.> I will keep a sharp eye (I can't sleep the way it is). Should I add a bit of salt? <No.> Stress-zyme? <No.> Is there possibly a metal in the water that Aqua-safe is not removing? <Not likely that this is what's harming the animal, if anything. I would suspect a poor reaction to a sudden change in pH above all else.> I always appreciate your help, thank you in advance. ~M <All the best, -Sabrina>

Black ghost knife fish 10/12/05 Hello guys just thought of saying thank you for all you useful info. <And thank you very kindly for these words.... It is great to hear/read this, some times.> I had a 55 gallon fresh water planted tank that was running for about 2 and half years. Fish in the tank: 1. a black fin shark (5") <Gets very, very, VERY large with time....> 2. a black ghost knife fish (8") 3. 2 adult angels, a marble and a golden (3" in diameter) 4. a rope fish (8") 5. a Pleco (5") 6. a stripe Raphael cat (4") 7. 3 tiger barbs (2 ½") 8. 2 ruby cichlid (2") <A touch overstocked for my tastes! Just be sure to keep up with water quality....> It wasn't until two months ago that I started having trouble. I acquired the 3 tiger barbs from the fish store when I normally go. Some lady came in and left two containers full of huge fish, between them was the three tiger barbs that I took. I introduced them to my tank without using a quarantine tank the way I should have. <Ohhhh, no.> One of the barbs became really fat. After reading a little I thought it could have been pregnant. About three weeks later I noticed that it had cloudy eyes. They cleared after a couple of days, but it came back and ended up dying a few days later. <Many possibilities, here; including mycobacteriosis....> Now one of the two barbs left started chasing the other and nipping on its fins until it almost had none. So I decided to get three more tiger barbs to keep them in odd numbers.  <Very aggressive nippers; watch that they don't harass the other fish as well.> A few weeks later I noticed my golden angel had this white dust on its body. After reading I found out it was velvet. <Aaaaaargh! Serious bummer.> When I looked around the tank the black fin shark also had it. I did a 40% water change and treated the tank with copper. <Oh, yikes! Toxic/deadly to some of the fishes in your tank.> Kept the temperature on 80*. Next day the angel and the shark died and most of the other fish after that. I decided to get a 20 gallon set up and keep the fish that weren't sick (black ghost knife fish, the Pleco, and the two ruby cichlids). <Surprising that the knife and Plecos survived the copper - delicate fish.> I've done the constant water changes to fight the ammonia spike and it's been pretty good so far. But now I notice that the black ghost knife fish bottom jaw looks like it is decaying. I wish I could show you a picture. <I wish so, as well, but am pretty certain this is water quality related. Be sure to maintain ammonia and nitrite at ZERO, nitrate below 20ppm, with water changes.> Could you please tell me what could be wrong now? Cordially, Ivan. <Though it's entirely possible that these fish did contract velvet, I would lean more toward an environmental issue with this deterioration. Improve the water quality, and observe very, very closely.... and, as you've learned, in the future, quarantine all newcomers to your tank. Wishing you the best, -Sabrina>

Just general random questions about Knifefish... heh Hey there! First off, I'd like to say that I'm completely Wowed by your extensive and totally awesome information and help on all sorts of fish and such. It's been a great help to me, and quite interesting to read (heh, I'm a bit dorky =P) <You're in good company here> I've had fish for all my life really, and I'm always trying new stuff, so naturally, when I spotted an odd looking fish, I snatched him up right away. Probably not the most brilliant of moves, but the shopkeeper assured me that he was what I could handle properly. (we've known each other for some time...) He sold him as a "Chocolate Ghost Knifefish". Upon proper research.... I couldn't find a single thing on them, really. ^^" I can't quite determine the species of fish he is (or she really, I haven't found many websites that are too helpful with sexing Knifefish.), but he LOOKS like a Black ghost knife... but with a longer face, brown-ish, and a yellow stripe and a white dot for a tail. He doesn't match up with Brown Knifefish either, he just...isn't. Are there such things as Chocolate Ghost Knives, or is he just a special brown? <Mmm, there are a few species of apteronotids this could be. Most often sold is Sternarchella schotti: http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=48027&genusname=Sternarchella&speciesname=schotti> It's been a good couple months since we got him, and he seems very healthy and quite lively and happy. We've been feeding him frozen blood worms, but I've recently wanted to change it up a bit, too. I heard full grown brine shrimp aren't particularly nutritious though...can we feed just hatched, or is that too small/meager to last them? <The latter> I heard frozen krill was a good choice; compared to blood worms, where does that stand? <A mix of worms, insect larvae, crustaceans... live, or frozen/defrosted will do> When there's a downpour around our area, we often can find earthworms and such wriggling about, and our old fish gobble those up. However, we've been concerned that they may either lack nutrition, or possibly still have chemicals from landscaping/lawn work, is that a concern? <Yes> We often eat shrimp and seafood at my house, and though I know fresh shrimp are quite delicious and probably great for them, are the ones at supermarkets and such fresh enough? <Yes> You know, the ones laid out on ice, that are already dead? <These are fine> Or will only the live ones, until the hour before you eat, okay? <Will learn to take bits of these> Can they OVEReat? <Can, but not common> He seems to bloat really easily while he's eating, and because I'm concerned with him overeating, I normally give the rest to our other fish. However, the few times he does get to try and eat a lot, he seems to stop himself. Do they always stop themselves before they explode =P, or should I be careful with feedings? <One should always be careful here> Since he's been with the same tank for a while now, but I suppose I should check in while I have the chance, right? He's about 7+ inches, in a 46gallon tank. A blue Gourami, a gold Gourami, a red-tailed shark, a Pleco, and 2 angelfish. The fish are all about 4-5 inches in length. He's not terrorized by any of them, never seen a mark on any of them, asides from the gouramis always having spats between themselves. Any problems with these? <Should be fine> The tank is well planted, with aged driftwood, a ton of leafy plants, an excellent&powerful filter, more plants, and err...more plants. =) No little tunnels for the Knifefish like I've read about having, but he seems to like the plants enough anyways. Should we find a suitable tunnel, anyways? <Mmm, not necessarily... I like transparent... glass "chimneys" or plastic... for viewing... but the plants are fine> Wow. Typing wayyyy too much now, sorry! ^^" For now, my mind has run out of pathetically inane questions to pester you with, so until later.... Thank you for all your help! <Thank you for writing, sharing. Bob Fenner>

Black ghost knife problems? Hi Robert, I'm a bit worried about my new BGK (my new favourite fish!). I am currently setting up a new tank after becoming addicted to my boyfriend's set up! New tank is 80 litres, planted and has a fine gravel substrate. It is currently stocked with 2 Pearl Gourami, 2 Angels, 3 Tiger Danios, 2 Corydoras sterbai and a small (2.5 inch) BGK. <This IS small!> Tank is two weeks into its first cycle. <Yikes... Knifefishes don't "like" new systems... Hard on them to go through their initial chemical, biological changes> The BGK has been in for 3 days and while it seemed happy in the first two (hiding amongst plants) but I have come home from work today and it doesn't seem right. It is sort of hovering around the bottom of the tank, moving around almost like a drunk person. It kind of wobbles around a bit, then rests and then wobbles around again. It has plants to hide in, as mentioned, and also a piece of driftwood to go under but it doesn't seem interested in this. <Mmm, well, this is pretty standard behavior for the species... but... do you have another, older system you can/could move it to?> At the LFS it was happy hiding amongst Java Moss and seemed unconcerned with the lit tank (I'd watched it there for a couple of days and it seemed very strong and healthy). There are really no other signs/symptoms except this apparent listlessness and my gut instinct (and it appears to be easily caught in the relatively light current and moved along which wasn't happening yesterday). I checked the water parameters and everything was fine - Ph 7.0, temp 26C. Nitrite was very slightly elevated but not of note (I have added Amtrite down to fix this.) <Mmm, only temporarily and at a "cost"... as stated, Apteronotus don't like "going" through cycles> Is it just acclimatizing or do I have a problem?? <Perhaps both> Please help, I was really impressed with what I've seen on the site and decided you're the man to ask! Thanks. Alia <Best to move the specimen to an established, similarly peaceful setting, second best to be very careful of not feeding much, urging your completion of biological filtration (Please see here: http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm.  Bob Fenner>

Black Ghost Knife, yellow water, killing fishes I have a couple questions for you, I hope you take time in answering mine. I  see you do take a lot of care in the questions people ask. Here's one; I am wanting to buy a black ghost knife fish. Is this fish territorial? I  already have a loach in here and I don't want them to fight. <Likely will get along> Plus we don't want to buy pellets or freeze dried food, so will it survive on flakes? <No> My loach has been surviving for a couple months without those foods. <Won't be healthy on nothing but flakes forever> My second question is, my tank is getting yellowish color really fast and we clean our tank (55 gallon) like once every 2 months. What is up with that? <Need to do more frequent, partial water changes, maybe weekly... and possibly use carbon in your filter flow path> My final question is, my fish seem to be swelling up really badly, and then just die. I put in some medicine.  Is this what you call ich, if so what is it and how do I stop it? Thank you. <... time to study... and adapt a better maintenance schedule... It sounds like your system needs more regular care... likely your fish deaths are due to poor husbandry, a lack of nutrition, perhaps mis-medicating. Take a read over our website: http://www.wetwebmedia.com/FWSubWebIndex/fwsubwebindex.htm re Set-Up, Knifefishes, Maintenance... IF you want to be successful at keeping an aquarium you need to learn more re what it takes to care for it. Bob Fenner> 

Mainly Black Ghost Knife questions Hi and thank you WetWeb staff, My fish are doing great, after a very scary introduction. No one died and having been doing great (refer to suddenly stocked tank on WetWeb).  Well just a few questions, if I may.  But for reference I have a 55gal with Emperor 400, heater, etc., lots of (fake) plants, semi- fine (1/8" or smaller) substrate, a few rocks of different shapes making caves, heated to 80F, 7.8 PH, all levels great. a 8" BGK <Black Ghost Knife> a Pleco 6" 2- Blue Gourami (or Opaline Gourami not to sure because they have changed colors since I got the new one) a 4" and 2". a tiger barb 1.5" a clown loach 1.5"(just got him) a zebra loach 1.5" a ????? frog .75" I feed my fish a very wide variety of foods on a change by day basis.  My BGK has always been black and yellow I researched why because what I had seen was they should be white, I think on your site I was reading that some BGK are of a yellow variation. <Yes. this is so> Well my question is since I got mine a month and a half ago, he has started to turn whitish starting at the bands on his tail? I don't know why, I know that where he came from he was poorly fed and in a bad environment. Well Are there yellow variations or not (just mistreated BGK)? <The white/yellow markings do change with diet, water quality> My next question(s) is.  I now have 2 blue gouramis how long will it be before they will reach sexual maturity?, <A few months> I know they're bubble nest builders but have never seen them do this. I have lots of plants. is it a comfort level or something? <In part... also, the motion in the waters surface, the presence of other fishes> they seem to be very happy, the most aggressive feeders in my tank (other than the BGK at night). what I'm getting at is if they will\can breed? <Doubtful, unless given a calm, warm setting... on their own> I cant find anything on sexing them so I don't know. <Search the Net, books... not hard to discern if of size, maturity> and at the same time can my loaches possibly breed? <Can, but rare... they do get BIG (a foot or so)...> They are inseparable.  I would also like to get 1 or 2 Bala sharks (I am going to be getting a new 125gal in September and plan a move) will they get along with what is in my tank? What else is a possibility for moving fish? Thank you all for the site and personal help, James <Yes, and many choices. Bob Fenner>

Ghost knife? Hi there guys,<Hi Guru, MacL here with you.> Absolutely love your web site.. I was wondering if you knew what size tank I would need to get my ghost knife to grow to its full length, and also roughly how big it would get in a 900L tank (approx 240 U.S. gallons and  200 UK gallons). <Guru I need a little bit of clarification. Do you mean a black ghost or one of the other types of knife or bony fishes? If you take a look here you might find your answer, otherwise if you can clarify for me a bit we can go from there. http://www.wetwebmedia.com/FWSubWebIndex/knifefishes.htm> Regards Guru

BGK tank mates Hello, I have a Black Ghost Knife that I've had for about 5 months, about 4 inches.  He shares a 60 gal. tank with my Pleco and 2 Platy's.  I have a Fluval 404 for filtration and maintain the water regularly.  I'd like to get bigger, livelier, compatible fish for the Pleco and BGK.  I have a feeling the Platy's will eventually be food for a larger fish.  I'd love to get an Arowana but think it will outgrow the tank too soon and eat my BGK.  What about Oscars, Eels, Catfish, Red Tail Sharks?  I had a clown loach before but it was very spastic and swam anxiously in circles and eventually died.  What fish and how many can I add to my tank that would be best fit for the BGK and Pleco?   Thank you. Kristen <Hello Kristen, I'm afraid for what you want to keep in your 60 will certainly exceed the capacity of the tank when the fish get larger.  Keep your BGK and your Pleco and maybe add a red tail shark.  James (Salty Dog)>

Re: BGK tank mates Thank you James.  If I only add the red tail shark, is that enough for a tank of this size?  I've heard that I should be keeping 9 fish in my tank at all times for natural bacterial purposes.  Are there any other fish you would also recommend? Thanks again. <Kristen, Both the black knife and the Pleco will grow quite large so I am basing that on future growth of the fish unless you plan on getting a larger aquarium in the future.  The main thing is to monitor your ammonia levels.   When you add a new fish, check these levels for a week or two to make sure the biological system can handle the extra load.  James (Salty Dog)>

Black ghost knife with ich Hi I have a Black ghost knife fish who is a new addition to my tank - though I have owned them in the past and have learned the * hard way* that these fish need a lot of individual care. <And don't "like" ich medications> through research and experience, there has been a great learning curve for me -  My tank is 29 gal with only 5 other fish who have been stable and healthy ( 2 are Discus and healthy). <This tank is way too small for even just the Knife... or one Discus> 2 days ago, I bought a 4 inch BGKF who has a great personality but the aquarium shop I got him is only 75% reliable  - has a fair number of unhealthy fish)- my tank has been quite healthy and I do 30% H2O changes every 2 wks w/ gravel vac. <I take it you did not quarantine this new addition>   Today, my BGK started to show a number of ich spots - I killed my last BGK with Rx in the main tank for another sick fish - <Very common> (ironically - the 1st discus I got had a good case of hole in head!) I bought this fish because I loved the personality of this fish... - I need to *save him* - what should I do? all readings on my tank are normal ; ph is 7.8, Soft H2O, lots of hiding places sterilizer always running. Peggy <Please read here: http://www.wetwebmedia.com/FWSubWebIndex/fwich.htm and the Related FAQs (linked, in blue, at top) and: http://www.wetwebmedia.com/FWSubWebIndex/knifefishfaqs.htm I would use half doses of AquariSol, elevate temperature to the mid-80's F... And get a larger system for this life ASAPractical. Bob Fenner>

Knives, Spines, Rope and Fire. OK to add Claws? Hi, thanks for the info that you've given me so far, but I've got another question. I've got my 130 gallon tank set-up with a 10" clown knifefish, 12" spiny eel, 6" fire eel, and 12" Ropefish. <No guppies or swordtails for you, huh?> I also own two African clawed frogs (about 4" long each) that are being kept at my mothers work. I'm wondering if I would be able to put the two frogs in the 130 gallon tank. In your opinion, do you think that the clown might decide to take a bite out of the soft, fleshy frogs, or would he leave them alone? Right now, the clown eats 3" long goldfish, but I'm trying to get him to accept frozen shrimp. <A bit risky, IMO. A Knife will eat anything he can fit in it's mouth. Even if he only tries, he may kill or injure the frog. Not a great mix. Risk would be reduced if the Knife was off live food first and kept well fed. The eels may even cause problems at night, but less likely.>     Also, one other question.  For my 130 gallon tank, would a Classic Eheim 2215 canister filter and a Fluval 404 canister filter be enough for the tank? I'm going to be adding more fish to the tank than I have now and prefer to have above average filtration. If the filtration isn't enough, what's a good filter that I could add to the other two? <Each are rated for around 100 gallons. You should be fine as is, but those are some pretty large fish in there, and growing. I'm a big fan of Marineland's Emperor 400 for bio filtration. Surely wouldn't hurt to add the bio wheels to help with ammonia processing.> Thanks for all of your help. <One last point, which I'm sure you knew was coming. Try very hard to get the Knife off live fish. Hard to do, I know. But unless you can QT the feeders, sooner or later you WILL (not "may") bring Ick or some other nasty into your system. Treating a 130 with these large fish will be a challenge to say the least. Don>

Ghost knife fish Hi,     I'm totally new to keeping fish ..... Recently, (about 2 days ago) I bought 2 knife ghost fish and a new fish tank for them .... I did not do research before buying them. So here's the problem ... the new tank is totally empty .. I haven't had time to go get those "hiding" places for them .... Only place they hide is behind a pump in the tank and they seems to be fighting for the space ..... Do I have to separate them using a partition in the tank ? Also one of the them had the fin like "broken" that like hair .. not in one whole piece as like the other... is there any wrong with it ? and what should I do ?, < Black ghost knife fish are nocturnal (feed at night), so they don't thrive in brightly lighted aquariums without suitable places for them to hide during the day. You really don't have to separate them as long as you give each of them their own shelter to go to  during the times you have the lights on. Get a couple pieces of PVC pipe from the local hardware store and throw it in there for now and they will be fine . Although the tank will not look to good with a couple pieces of white pipe in it.-Chuck> Thanks a lot Chasel

Re: Attempt to save Ghost knife fish Hi,     Thanks for the last reply. However, I'm sending this out in attempt to save my fish. I now have a tank with some plant and a log inside, 2 black ghost knife fish and a swordtail. They live fine with each other and I had been feeding them with flask and they ate them. < Sorry . don't know what flask is so I don't know the significance is if the black ghost knives ate them> But just yesterday, I notice my 2 black ghost fish are not doing well. They aren't moving much even when I turn the light off ....and not feeding either. I have no idea why this is happening. I don't have any tester to test the water condition. My last water change of 30% was 5 days also. They were still fine then. I don't know what else I can do. All I did was a 30% water change this morning hope to save them. Any similar situation to help ? < Well I guess we need to determine if their behaviour change is a symptom of something more serious. Try feeding some California Blackworms, often called Tubifex still at some pet shops across the U.S. If they don't go for this look carefully for signs and symptoms of some things we can specifically treat. I really don't like to medicate a tank if it is not needed. In the meantime make sure that the water is up about 80 degrees F and the filters have been serviced and do another 30% water change. This should take care of any water quality problems. If the fish don't respond then I would remove them to a hospital tank were they can be observed more closely and look for symptoms.-Chuck> Thanks Chasel

Re: Attempt to save Ghost knife fish, II Hi,      Its was a typo on the food I feed them. I meant flake. But anyway, one of them is dead and the other one is laying on the floor now. I did another 30% water change, no use. I move the last one to another tank with and 80% fresh water no use either. Thanks anyway < Black ghosts like warm acidic water and usually don't eat flake food. If the water they were kept in was hard and alkaline then their kidneys may have failed due to an imbalance of  minerals in their system. Hard to tell. Sorry about your fish.-Chuck>

New to Knives 8/2/04 I'm new on the knife fish thing so you might need to help me. I don't have any current problems but,  I want to know if three glass knifefish  in a 55 gallon tank is ok. < These fish have weak electronic organs and when they are kept together they seem to always be bickering  amongst themselves. They don't do any real harm to each other so if you have plenty of areas to hide then they  should get along fine.> Males grow about 18" and females 11". A fish manual says 1" per gallon that would be 54"  with three MALES. Here's the question. How do you tell male from female when they are the same size. < The books all say that the males get to be the larger fish. They are somewhat transparent so look for  differences in the body itself. You may not see any until they get close to adult.-Chuck> They are about 4".((I have other fish in there already.))  Please Help If Possible. Thanks.

Black Ghost Knife Help Hi there from another fishaholic!<Hi Jennifer, MikeD here> Sorry to bother you with petty questions that really don't apply to any of your other visitors, but I *really* need some help regarding my black ghost knife.<One of my all time favorite FW fish> Although I generally research fish species very thoroughly before purchasing them, I only did a little such research before buying a black ghost knife. It was really pretty much an impulse buy, though I was at least somewhat familiar with the species.<They're pretty tough if handled right> At any rate, the manager of my LFS promised me that if I purchased one, he would do just fine in a twenty-gallon, provided he had plenty of coverage and was kept completely by himself. She did say that it was pushing the limits to keep him in a 20-gallon, but that he'd do okay, even as an adult. (He's 7 inches now.)<I'm not sure why they told you to keep it alone, as they do well with many other species if the tank is arranged correctly. As to the adult part, my largest grew to about 15" if that tells you anything> Now, I'm starting to have second thoughts on that. I assume he's okay for *now* in the 20-gallon, but will he really be okay when he grows up? I have an extra 35-gallon that I haven't stocked yet but it's very well planted and decorated, as I tend to pride myself on that. The problem is, it's very hard, brackish water, and it would be a huge inconvenience to redesign and refill the whole thing. Besides, I was really looking forward to the archers and Sailfin mollies I was going to keep... But, if I need to, I'm willing to change conditions if that's what it takes to save my ghost knife. (I simply can't afford another large aquarium for him.)<OK. While he WILL eventually outgrow the 20 (20L or 20H?), they are fairly slow growers so you've got at least a couple of years before it should become a concern.> Wow, you're very patient if you're still reading this.<Still here **grin**> I guess, to get to my point, can my ghost knife stay in that 20-gallon as an adult, or even now? Or will I have to completely revamp the 35-gallon for him? Would a 35-gallon even be enough? Should I just swallow my pride and give that poor fish to somebody that can take better care of him? Just how fast will he grow, anyway? Maybe slow enough that he could stay in the 20-gallon until I could afford a new tank?<I guess I should have waited until I got here to answer, eh? **grin**> Also, the LFS lady told me that black ghost knives can be held and are even intelligent enough to recognize their handlers... is this true? Sounds a little odd...<It depends on what she means by held. If you cup your fingers in the water, they will indeed swim into your hand if you train them.  I don't know what you're currently feeding it, but they also appreciate meaty foods, with their favorite being earthworms. They'll also appreciate ghost shrimp and even a piece of raw shrimp like you'd have for dinner, unbattered, of course.  These are small cousins of the electric eel, and I'm assuming you know that they navigate by true electronic sonar. Because of this, never add another S. American Knifefish or African Mormyrids, such as "baby whales" or "Elephantnoses"...they cross each others electric signals and a true war will result> Thank you SOOOOO much for your help! <You're very welcome>

Ghost knife with cichlids My son has had a black ghost knife fish for four years. He is about 9 inches.  We, being ignorant, were keeping him in a <gasp> 10 gal. aquarium all this time. <yikes that is a bit small...> The last few months he ("Sonar") would stay out of his ghost tube most of the time and do loops a lot.  We increased his feed. <that happens with Knifefish small tanks seem to have them get restless.> Anyway, at Christmas I bought him a 29 gal. tank <wow> thinking that would be wonderful.  It came with an Aqua-tech 20-40 power filter. <I know you're laughing>.   <Any filter is better than none, just have to make sure the water parameters are okay.> Being ignorant again, in regards to the new tank cycling.  I also bought two convict cichlids to keep him company.  My thinking was they could hold their own with him since he killed the Neons and Bala shark my son used to have.   <be cautious with any cichlids and Knifefish, cichlids are nippy things, and if a Knifefish should loose his anal fin (which is it's only real propulsion) then it is done for.  I try to keep my Knifefish with tankmates that I know won't bother it.> I used the Stress-coat and Stress-zyme.  The ammonia levels got really high.   <A fish that size is bound to put out some high amounts of waste and ammonia> I did have a knowledgeable man at Petco advise me on changing out the water and doubling up on the stress-zyme.  So I did that two times the first week, about 25%. <The stress-zyme isn't really helping the ammonia levels, it's helping the water additives in your water.  The water change is helping the ammonia levels. So keep up on the water changes.> I kept asking about using our filtered drinking water  at fish stores and no one seemed too concerned.  We have rural chlorinated hard water but a water softener, which is what I used for the tank.  I now plan on using the filtered for the next change out. <many Saltwater people prefer using filtered water for their tanks, nothing saying you can't use it.  Just that it can get expensive.> Should I still use the chemical additives? <It's not hurting the fish any, so you can keep doing it, just only add what is recommended on the package.   Good luck with the knife.  When they get older you will have lots of fun.  I have a friend that feeds his ghost by hand.> My main question is should I get rid of the two cichlids?   <I would, they run the risk of damaging the knife.> Since all this I have spent a lot of time reading and learning ( a good thing) about these guys. <That is a very good thing.  Research research research!  you will have more fun if you know what to expect.>   I think they are both males.  The bigger one (they're both about 3 in) chases the other a lot and so he hides by Sonar which is sometimes in his tube with him.  I just noticed a couple slits in Sonar's ventral fin now and I'm feeling very guilty.  Other than that they seem to not bother him.  He still does his loops and does come out to feed when the light is on although he is spending more time in his tube again. Also, I have learned we really didn't have a biological filter so I stuck a trickle filter sponge in the power filter where the water flow out hoping that will help. <any more filtration is better than what is on there.> I'm pretty sure I'm going to find a home for these cichlids even though I enjoy watching them.  I thought of just getting rid of the aggressive one.   <You can set up another tank for them.  Cichlid tanks are extremely rewarding.  Get a male/female pair, and within 3-4 years you will no doubt be an expert and breeding them for you LFS!> Sonar is my biggest concern.  Should I do anything else?  Any suggestions you have would be greatly appreciated. <I would separate the fish, chances are high that they will pick at Sonar when you aren't around.  Give some thought into setting up a cichlid tank, I'm sure you and the family will really enjoy them!> Sheryl in Missouri     <good luck Sheryl.  -Magnus in New York>

Large Fish Compatibility I have recently bought a striped shovelnose and a black ghost together and the pet store said they were compatible, which they are. they don't bother each other. later on I bought a gold Severum and 2 clown loaches, which the pet store said that the Severum and clown loaches would go good with the black ghost knife fish and the shovelnose. nothing has happened yet because they are all pretty small. but I was telling someone what I had in my tank and they said that I shouldn't have listened to there advice because the black ghost knife fish would be fish food sooner or later. so I was wondering is that true? I do know that the Severum is compatible with all the other fish but I couldn't find any information on the black ghost fish. if you can help I would much appreciate it.         thank you          sincerely, Lindsey <Hi Lindsey, I am scared to ask what size tank you have.  These are all fish that get really large.  The shovelnose can get close to 2ft, and the Ghostknife will not be too far behind.  In a large enough tank you might be ok, I personally do not trust large catfish with smaller tank mates, they have a tendency to eat them.  You can find more on the Ghostknife at the links below.  Best Regards, Gage http://www.wetwebmedia.com/FWSubWebIndex/knifefishfaqs.htm http://www.mongabay.com/fish/knifefish.htm  >

Black Ghost Knifes Hello. I read the FAQ but I am unable to find the answer for my question. I have a rectangular tank is 16" x 9" x 11". But I have 2 ghost fishes. It is healthy for the fishes? I noticed that they sort of dance/swerve/bite each other in that sequence. I am afraid that they are trying to kill the other off. I bought a volcano rock (that's what the shop says) for the fishes to hide. Seemed like they don't share. Should I buy another one to keep the other happy? 1 last thing, the fishes don't eat the flakes floating on the water. Instead they scoop around the top edges of the tank. Thanks. I really those answer. Please <These fish need a larger tank, at least 55 gallons even that may not be big enough to house 2 of them, they are aggressive towards their own kind.  Check out the link below for more information on these fish.  Best Regards, Gage http://www.mongabay.com/fish/knifefish.htm  >

Black Ghost Fish Hi   <Hello> I   am setting up a tank for a ghost fish and want to know what sort of plants are good for putting in the tank and what other fish are suitable if any <Tropical South American plants are my fave... ones that would, could be found in the same habitat. Tropica has a nice website that shows some of these biotopes... and maybe some sunken driftwood. Many medium sized Characoids (tetra) fishes will go with this Apteronotus... as well as Callichthyid catfishes... even angels. Bob Fenner> Cheers Shelley Molloy

In Love with a Chocolate Ghost Knife Hi Bob, <Hello Susie> I have recently (three weeks ago to be exact) set up a freshwater (20 gallon) tank. My daughter has four aquariums, and has been quite successful with her fish. I went to her "fish place" to purchase a few new fish and fell in love with a chocolate ghost knife. <A beautiful and intelligent species> The owner of the shop assured me he would be fine with my mollies (5), guppies(6), Platies(2), Cory cats(2), red tail shark(1), silver stripe shark(1), leopard algae eater(1),and Neons(4). He is about five inches long and he is beautiful! I would really like to keep him, but now I have read on some internet sites that this may be bad. He seems to be fine, and prefers a rock cave to his clear tube. My questions are : <Well... it will likely eat all baby livebearers... and your Neons in time... And the "sharks" prefer different water quality... hard/alkaline versus softer/acidic... and the worst fact to relate... your tank is way too small for all these fishes.> 1.Did I make an incorrect purchase? 2.Will he kill my other fish? 3.How does he find his food (bloodworms are what the guy suggested). 4.Does he absolutely have to have live food, and if so, what should I give him. <Not live food, frozen defrosted meaty foods will likely do... offered right after "lights out" for the Ghost...> I would really like to keep him, but I do not want to do the wrong thing. <There are many other things to know about this fish and its relatives... they don't tolerate much in the way of standard fish medications... are electrogenic... Bob Fenner> Susie

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