FAQs on Knifefish Identification

FAQs on Knifefish Identification

Related Articles: Knifefishes, Gymnarchus, Black Ghost Knife, Electrogenic Fishes,

Identifying knife fish 12/1/16
Hi my lfs recently ordered a fish for me. At first they said it was a mousehead knife but after doing some research I discovered that there is one called mousetail however when the owner talked to the distributer they said it was a granite knife so i did research to make sure i could take care of it properly. Unfortunately it was not a granite. I have searched
the internet and can not find what it is. It kind of resembles a ghost knife. It is about 8 inches but really thick. He's black with a stripe on his back like a ghost knife however his tail looks speckled with white. It kind of looks like someone threw paint on the last couple inches of his tail. His mouth looks similar to a ghost also but it looks bigger. I would take a picture but he's hiding. If you have any knowledge on what he could be i would appreciate it so much. I want to take care of him properly. I have him in a 45 gallon which is too small for him but i wasn't expecting to get one quite so large so i thought i would have time to save money to buy a bigger tank. Hope to hear from you soon. Thank you,
Jessica
<Hi Jessica. Really do need a photo here. If the fish has a stripe along the back, but isn't as black as Apteronotus albifrons, it might be one of those sister species imported less often, such as Apteronotus leptorhynchus or Apteronotus bonapartii. Alternatively, the Granite Knifefish name has been used for certain Steatogenys species. These are mostly smallish (around 30 cm/12 inches) species, a bit delicate with regard to water chemistry, though otherwise unproblematic fish occasionally maintained by expert fishkeepers with access to live or frozen foods. Cheers, Neale.>

Identifying knife fish... 26 megs....       12/18/16
Jess; have deleted your email as it uses more than half our allowed bandwidth/space. Please resize your pix to a few hundred Kbytes and re-send all. Bob Fenner
Re: Identifying knife fish      12/19/16
Hi I'm not sure how do that. Would it help if I uploaded them to Imgur and sent you the link?
Jessica
<Ah yes; thank you. That will do splendidly. BobF>
re: Identifying knife fish      12/19/16
For some reason the WWM emailer is cropping my message. Pasted below.
Cheers, Neale
--------
<<I would also have you use the tools at *your* disposal; assuming these are South American, then review the families within the Gymnotiformes, excluding the highly distinctive Electrophoridae (one species: the electric eel). To wit; Fishbase; the family entries, set to show photos of the species; some are blank, but such fish are unlikely to be traded. A powerful tool that takes a few minutes to learn, and what I would probably end up using to identify your fish if it isn't obviously one of the commonly traded species.
http://www.fishbase.se/identification/specieslist.php?famcode=545&areacode=
http://www.fishbase.se/identification/specieslist.php?famcode=546&areacode=
http://www.fishbase.se/identification/specieslist.php?famcode=547&areacode=
http://www.fishbase.se/identification/specieslist.php?famcode=548&areacode=
These families/this order is pretty consistent. Assuming it isn't one of the big predators (Gymnotus spp. for example) these are medium-sized, territorial but fairly to very social (in groups of 5+) fish; fairly to highly sensitive to poor water quality and low oxygen level; timid; nocturnal; usually picky feeders with a requirement for live or frozen invertebrates rather than flakes/pellets. Not difficult to keep if their very specific requirements are understood (well oxygenated but deep tanks; ideally with low to moderate hardness, acidic to neutral pH). Eigenmannia virescens is very typical of the majority of species, rather more so than the bigger Apteronotus albifrons, which is more routinely kept. Commonalities to both outlined above; many sold, many bought, few survive more than a few months in either case. Poor to non-community fish; not impossible to keep, but do require some thought, understanding and experience. Cheers, Neale.>>
Re: Identifying knife fish      12/19/16
Hi Neal, thank you for those links however he is not like any of those pictures. I had sent a few pics of him but I guess they are too big so I'm trying to figure out how to upload to Imgur and I will send you the links.
Thank you,
Jessica
<Mmm; Jess; there are a few ways to re-size images... One simple online program here: http://imageresize.org/
Do you use/have a Mac or Windows machine? BobF>
Re: Identifying knife fish      12/19/16
Hi Neal, thank you for those links however he is not like any of those pictures. I had sent a few pics of him but I guess they are too big so I'm trying to figure out how to upload to Imgur and I will send you the links.
Thank you,
Jessica
<Understood. As/when you have some photos uploaded or mailed to us, I'll take a look. Cheers, Neale.>

Re: Identifying knife fish 6/20/16
Hey I uploaded it online instead because I don't have a computer and here's the link.
Knife fish https://imgur.com/gallery/2cCgk
Jessica
<These really are too blurry, Jessica, to do much with. The shape of the tail (e.g., does it end in a thread-like extension) is important, as is the shape of the snout (e.g., is it robust and rounded, or drawn out into a beak-like shape). Can't see either of these features. I'd be looking at Gymnorhamphichthys, Rhamphichthys and Steatogenys in the first instance,
seeing what Google throws up. I'd also look at Gymnotus species too, though these are usually bigger and certainly more aggressive fish. At the end of the day, while Gymnotus is a fairly tough fish, all the others are fairly to very delicate fish that can't be weaned onto pellets or flakes, and do need highly oxygenated water to do well. So there's really not much to say about individual species, and maintenance is very consistent. Some variation in adult size, but most are fairly small, 30 cm/12 inches tops, the exceptions being Apteronotus spp. Cheers, Neale.>
Re: Identifying knife fish
Hi did you guys get the link I sent? If not I'll send it again. Thank you
Jessica
<Do check your email in box; have replied. Cheers, Neale.>

Re Identifying Knifefish 1/7/17
Hi guys, so awhile back I had sent you guys some pics of my knife fish but unfortunately they were too blurry but finally I got some good shots and uploaded them to Imgur. I'm really hoping you can tell me what he(she) is since I have spent countless hours on the internet and talking to others in the hobby. Hope to hear from you soon.
Jessica
https://imgur.com/gallery/4e7WE
<Not 100% sure, but think that this is Apteronotus leptorhynchus, also known as the Brown Ghost Knifefish. Basic care identical to the Black Ghost Knifefish, but looks a bit different and only gets to about 30 cm in length. But does have a similar beaky-sort of face to the Black Ghost. Does the fish have a pale band running along its back? If so, definitely
Apteronotus leptorhynchus. Has the 'flag like' tail fin of Apteronotus species though, and looks to be a fairly big fish, which again accords with Apteronotus. By contrast Gymnotus species have tails that taper to an almost needle-like point. Let me direct you again to Fishbase, the Apteronotidae species list, which has photos at top and also a list of
species with standard lengths at the bottom. Should help you.
http://www.fishbase.org/identification/specieslist.php?famcode=545&areacode=
Cheers, Neale.>

Re: Identifying Knifefish 1/8/17
Thanks for getting back to me Neal,
<Welcome.>
I really appreciate it! I looked at the brown ghost knife and he does look similar however the stripe that runs down the body starting at the mouth is not the same on him. He has a very light line but it doesn't start until the back of his head and it doesn't run down his entire body to the tail.
<So I think we can agree he's related to Apteronotus leptorhynchus, if not quite that species.>
Also his coloring is definitely different than the brown ghost knife. He is black/grey with white splotches down the bottom half of his body. As you said he is pretty large and his width is 4 inches and he's about 11 inches.
I have him in a community tank right now because I started a new tank for him but I'm in the middle of cycling it right now and I don't want to put them in it until it's done cycling so he's in with smaller fish and he's very peaceful with them except sometimes they won't leave him alone going in his cave so sometimes he uses his head to ram them out.
<Standard operating procedure for most electric fish, to be honest!>
I also saw him open his mouth once and it's huge!
<Do please check Gymnotus as well as Apteronotus; the two are fairly similar in body shape, though their tails are different. Gymnotus has a big, big mouth -- as befits a confirmed fish-eater. Gymnotus also tend to be territorial and aggressive, which doesn't sound much like your chap, but on the other hand, a variety of Gymnotus species are commonly traded, most of which lack common names.>
I was wondering if it's at all possible that he's a hybrid?
<Possible.>
Would different species of knife fish spawn in the wild?
<Yes, but it's uncommon for all sorts of reasons. Still, it does happen.
What is more likely is a related but different species of Apteronotus, or a subspecies of Apteronotus leptorhynchus even.>
I know most don't care for the company of each other but he looks so different than any I've seen. His head kind of looks like a dinosaur.
Thanks again for helping me out with this!
Jessica
<Cheers, Neale.>
Re: Identifying Knifefish; now fdg. 1/8/17
Neal, thanks for such a quick reply. So I have one more question. I feed him live black worms which he happily slurps up. Is there any other foods I can give him?
<Definitely needs more variety than this! I'd be looking at earthworms and gut-loaded river shrimp as staples, and if he takes frozen foods as well, such as krill or Spirulina-enriched brine shrimp, that'd be great.>
Sometimes I have given him blood worms but I know they shouldn't be a everyday food. I won't do feeder fish as they carry parasites but what if I breed guppy's or something similar for him to eat or is this unnecessary?
<In theory home-bred Guppies are safe, but in fact not necessary, if for no other reason they're more likely to encourage him to view fish as food, which could cause problems for tankmates. In the wild Apteronotus are more
micro-predators than anything else, and benthic invertebrates such as insect larvae are probably their main food. They do have substantial appetites though, so do keep an eye on how rounded his belly looks.
Slightly convex is what you're after, rather than bloated, but shouldn't be concave either.>
I just want to give him what he needs and deserves.
<Understood and he looks a great fish! Big adult Apteronotus are impressive, and intelligent, animals that make rewarding pets. They can become quite tame, and electric fish often become rather quirky as they settle in, with distinct personalities. At least some species have brain to body weight ratios similar to mammals, suggesting a high level of intelligence, by fish standards, anyway. Cheers, Neale.>

Info on Sternarchorhamphus macrostomus. Platyurosternarchus (formerly Sternarchorhamphus) macrostomus 8/23/07 Hello all. <Hi.> Well, I do a lot of the ordering at a store I work at, and I managed to get in two Knifefish under the name 'elephant knives'. The species appears to be Sternarchorhamphus macrostomus, but the problem is I cannot locate ANY information on this fish outside of the limited info under the picture in Axelrod's Atlas. <Likely one reason is that the genus is considered to be Platyurosternarchus by some. Using this name will bring up more hits in databases and the net, although not as much information as you would certainly like to have. In addition a proper ID is not easy. Also have a look on other members of the Apteronotidae or Gymnotiformes in general (http://www.wetwebmedia.com/FWSubWebIndex/knifefishfaqs.htm).> I only managed to get 2, and I cannot get more, so I'm thinking very seriously of getting them for myself. <Certainly very rare if this species.> I was wondering if anyone here has any information on these fish. <Not much, but I'd expect it to be similar to more common ghost knives and other neo-tropical knife fishes. Likely will attain 15' and is slightly electric. Would not keep it with other electric fishes. Many occur in groups and use their electric organ to communicate, so I would not separate the two specimens you have. Small fish will probably be eaten. Plenty of floating plants would help them to feel comfortable, since many are nocturnal. Males are usually much larger. Breeding possibly can be triggered by imitating rain season.> They are feeding well on frozen/thawed bloodworms right out of my hand, and as far as I can tell are showing no aggression towards one another. <Great.> Thanks for any help you can give! <Have fun with your new fish. Seems you are doing some pioneer work. Marco.>

Steatogenys duidae Hello, I was wondering whether you might know anything about a certain Knifefish "Steatogenys duidae", I saw it listed as the Centipede Knifefish at "Zang exotic Fish Company" but can't find information about it anywhere else, (and i think a seller's information should always be treated as a little suspect just to be safe). I know you should always research a fish before you even consider buying it but this species has got me stumped. Would it work in a 55gal community tank? Thank you J Dunlap <Mmm, IS a valid genus, species of Hypopomid knife... I suspect it's care is very similar to the ever-popular Black Ghost Knifefish. On Fishbase: http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=48119&genusname=Steatogenys&speciesname=duidae A fifty should work out fine... subdued lighting, live foods, soft, acidic water, an absence of metal dye medications... Bob Fenner>

Ghost Knife Hi, I recently bought a new fish from a local pet store and he is doing just fine. The guy that sold it to me said it was a Black Ghost Knife fish, although the fish does not have a white stripe down its back or a white band around its tail. It does, however, have a very dark brownish red stripe where the white one normally is and no band of color on the tail. The fish's body is jet black. Is this a Black Ghost? If you know the answer could you email me back? Thanks! <Hmm..., not quite sure, do you have a picture? Check out Monga bay and Fishbase to see if you can find a match. -Gage http://www.mongabay.com/fish/knifefish.htm http://fishbase.org >

UFS (Unidentified Freshwater Specimen) Hello again, Mr. Fenner! On my yesterday's trip to my LFS I spotted in one of the freshwater tanks, along with some Discus, a black sort of "file fish" thin) around 2" long; it also had a white stripe near the head and a peculiar way of swimming, since it only uses a long ventral fin to do it. Not recognizing the species I asked the employee the name of it. The answer was: "It's a Roberty... but that's all I know!". Can you please give me any clue of it is, or a positive ID of this specimen??? <Umm, sounds like a "Black Ghost Knifefish" to me: Apteronotus albifrons. Please take a look on the net (at least fishbase.org) under these names. Bob Fenner> Thank You, best regards ! Luis Santos

Knife fish cheerleaders? (04/21/03) I have just recently purchased a knife fish from the local petstore. The fish was called a "Pom Pom Knife fish" but I have searched all over the internet and not found anything. <I'm finding a lot on knife fish, and even more on pom poms, but nothing about pom pom knife fish... nothing on cheerleader knife fish, either.> The fish looks exactly like the Black Ghost Knife fish but mine doesn't have the white tail and isn't electric. I was wondering if you might know of a fish that is quite similar to the Black Ghost Knife fish so I can see if it is what I have and find out how to take care of it. <Try this site for descriptions of several types of knife fish: http://www.mongabay.com/fish/knifefish.htm> Thanks, <You're welcome. --Ananda>

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