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FAQs on African/Brown Knifefish, Xenomystus nigri

Related Articles: Featherfin Knives, Bony Tongue Fishes, Arowanas, Arapaima, African Butterflyfish, Featherback Knifes, Mormyrids, ElephantfishesNew World Knifefishes, Black Ghost Knife,

Related FAQs: Feather Fin Knives 1, Feather Fin Knives 2, & by Species: African Featherfin Knife, Xenomystus nigri, Clown Knife, Chitala ornata, & Bony Tongue Fishes, Aba Aba Knifefish, South American Knifefishes, African Butterflyfish, Arapaimas, Arowanas, Mormyrids,


Xenomystus and Gnathonemus... stkg.; and tog.     1/22/16
I'm planning a 120 gallon for a group of elephant noses. I'm also considering a group of Xenomystus nigri, in addition to or replacement of the elephant nose school.
There is advice on your site about Xenomystus, that adults are territorial but not so much that it's impossible to keep a group.
<Can be if "crowded"; something like Mbuna cichlids...>
I also found a video of a public aquarium with dozens of adult Xenomystus, (it was much taller and bigger than a 120), they were active, and not avoiding each other. So I don't know what that says about their behavior in a smaller group and smaller tank.
<Ah yes; can be grouped here>
In a 120 gallon, how many Xenomystus could be added to a school of 10 or more elephant noses?
<About the same number>
Is their a similar approach with Xenomystus and Gnathonemus, keeping them in larger groups works and small groups leads to problems?
Or is Xenomystus less aggressive and a smaller group of 5 will live together peacefully?
<Not likely in this large a system... 2 or 3 would likely, or ten or more.
The Notopterids may well pose a problem of out-competing the Mormyrids for food>
Is a 120 with a group of both of these fish too crowded?
<Not likely; though incompatibility for food....>
And finally is it better to use a 4' x 2' x 2' 120 gallon, or the 60-72" long version that only has 18" of depth?
<For me, for these fishes, the longer and shorter... more bottom area>

Thanks, I don't know if combining these fish is best left to a tank bigger than a 120.
<Best to not combine, but use other, more mid and upper water fishes as tankmates IMO/E. Bob Fenner>
Xenomystus and Gnathonemus /Neale       1/22/16

I'm planning a 120 gallon for a group of elephant noses. I'm also considering a group of Xenomystus nigri, in addition to or replacement of the elephant nose school.
<They can coexist, given space.>
There is advice on your site about Xenomystus, that adults are territorial but not so much that it's impossible to keep a group.
<Quite so.>
I also found a video of a public aquarium with dozens of adult Xenomystus, (it was much taller and bigger than a 120), they were active, and not avoiding each other. So I don't know what that says about their behavior in a smaller group and smaller tank.
<Pairs and trios can be a bit unpredictable, but larger groups work better, especially in large tanks.>
In a 120 gallon, how many Xenomystus could be added to a school of 10 or more elephant noses? Is their a similar approach with Xenomystus and Gnathonemus, keeping them in larger groups works and small groups leads to problems?
<Correct; I'd not keep fewer than six of either, which 120 gallons should house perfectly well. A few more of either, as water quality and filtration allow, and of course depending on other tankmates, such as dither fish you think helpful.>
Or is Xenomystus less aggressive and a smaller group of 5 will live together peacefully?
<See above. Xenomystus may be irritated by the electrical signals produced by the Gnathonemus. So you want space, and I'd suggest a decent number of nice big ceramic tubes (or similar) where the Xenomystus can rest up, away from the Gnathonemus. There'll also be a fair amount of competition for food, and I'd definitely be getting youngsters that I could train to take frozen foods rather than older, more fussy specimens.>
Is a 120 with a group of both of these fish too crowded? And finally is it better to use a 4' x 2' x 2' 120 gallon, or the 60-72" long version that only has 18" of depth? Thanks, I don't know if combining these fish is best left to a tank bigger than a 120.
<Hope this helps, Neale.>

African knifefish  12/7/11
Hey there WWM crew!
John here with a follow up question about the African knife fish i hope to house with a school of 5-6 Toxotes microlepis.
Here's the stats of the tank as it just finished cycling about 2 weeks ago.
Ammonia 0
Nitrite 0
nitrate i think 15 ppm?
Ph: 8-8.2
My ph and hardness are just a bit harder and higher ph value than i would like. Would a ph of 8-8.2 be unsuitable for one of these awesome knife-fish? I know the African brown knifefish are pretty hardy as far as knife fish go...
Any input would be greatly appreciated!
<You should be okay, but see if you can reduce the hardness a bit. Don't worry about the pH directly. Optimal conditions would be a 50/50 mix of tap water and rainwater/RO. Even one part RO/rainwater to 3 parts hard tap water would make all the difference. Cheers, Neale.>

Knifefish Compatibility 3/4/10
I am still in the planning stages for my first tropical tank. I am planning on getting something in the 40-50 gallon range. I have been thinking about what fish to put in it. I would like to have an African Brown Knife, 6 or so Australian Rainbowfish, a school of Barbs (either Cherry, Rosy, or Odessa) I am afraid that the Knife Fish might eat Cherry Barbs or they would be my preferred species.
<Certainly a risk. Xenomystus nigri is a predator, and a nocturnal one at that, and while it isn't a huge fish, it does reach 20-30 cm/8-12 inches, so is big enough to see small tetras and barbs as potential snacks. Sure, it mostly eats invertebrates in the wild, but that doesn't mean it won't have a go at any sleeping fish it comes across. So I'd choose tetras or barbs that are a step up in size. If you want red fish, then something like Bleeding Heart Tetras or Red Rainbowfish (Glossolepis incisus) would be good choices. Rosy Barbs might work, but they're subtropical fish, and don't do particularly well when kept at tropical temperatures continuously.>
I would like an African Butterfly but I know I can't have Cherry Barbs if I get one though. Does this grouping sound as if it will get along, or the bigger question do they take anywhere near the same water parameters?
<Rainbowfish, Xenomystus nigri, and African Butterflyfish would all get along very well. I'd skip barbs to be honest, either in favour of a second Rainbowfish species, or else some sort of African characin, such as Congo Tetras. All should do well in soft to moderately hard, slightly acidic to slightly basic water at 25 C/77 F.>
I would also like a Pleco but would want a smaller species, would it be fine with the Knife?
<Generally, yes, Plecs get along fine with Knifefish.>
I had thought about Congo Tetras or American Flagfish but they are not readily available here.
<The Congos would be ideal. Florida Flagfish are subtropical fish really, and not ideal additions to this set up. If you wanted Killifish, you might try Aplocheilus lineatus, including the so-called Golden Wonder Killifish.
This is an Asian species, and though territorial, if the tank is big enough, a pair of them would work okay alongside the African Butterflyfish.
Both the Killie and the Butterflyfish are surface-dwelling lurkers, which is why they might fight over the best hiding places at the top of the tank.
Both species need floating plants or at least floating leaves, otherwise they won't settle down. They hate strong water currents, so a gentle corner with floating plants is what they want.>
I know that the knife needs safe hiding places and prefers a shady tank, I am planning on putting duckweed in to help shade the tank. Would putting in the duckweed be enough to cycle the tank?
<I'd skip Duckweed to be honest, and get some Indian Fern and/or Amazon Frogbit, both of which will speed up the cycling and also look MUCH prettier.>
Or should I put in a few fish to help it cycle, I don't want to cause the fish unnecessary stress.
<Add the plants, and then add some fish food, just a pinch, every day or two for the first 2-3 weeks. You should measure nitrite levels, and see that these go up and then drop down. When they drop back down to zero, you're ready to add your first few fish.>
Cheers! And many thanks!
<Cheers, Neale.>

Knife fishes... Xenomystus and BGK comp.    1/23/10
Hi guys,
It's been a long time since I've had a question for you. Everything has been going very well.
I now have a 240 gallon tank with a 6" diameter retic sting ray, 12 inch silver Arowana, 6" Bala shark, 5 ea. 2" clown loaches, a 5" African knife, and a 5" black ghost knife. I read somewhere that it was not a good idea to
keep the two knife fish together. I'd like to hear your opinion/experience on the subject.
<These two Knifefish are very different in terms of habits, so should cohabit reasonably well, providing each had space and a suitable cave.
Apteronotus albifrons is an electric species, and yes, in captivity small groups are prone to bullying. This is common to electric fish, in part because they "jam" each other when confined in small spaces. Apteronotus albifrons may be kept singly, or else in large groups of six or more specimens. Xenomystus nigri is not an electric species (though it may well detect electrical fields generated by its prey). Although territorial, it is not nearly so aggressive as its Asian cousins in the genera Chitala and Notopterus. Those Asian knifefish really do need to be kept singly once sexually mature, the males in particular being notoriously defensive in the wild, supposedly biting at humans who wade too close to them! By contrast, Xenomystus nigri is comparatively easy going, juveniles at least being gregarious, adults territorial but not much given to tantrums if allowed space to themselves. Hope this helps. Cheers, Neale.>

Re: knife fishes 1/25/2009
Thank you!!
<Most welcome. Neale.>

African Knifefish 01/17/10
Dear Crew,
I have an African Knifefish named Switch, and he/she is currently residing in a 30 gal. freshwater tank. I am a bit concerned because his sense of direction appears to be nonexistent in that he runs into EVERYTHING in the tank.
<May simply be nervous; do switch the lights off when introducing this fish, keep the tank shady the rest of the time, and do not keep with aggressive or nippy tankmates.>
I know that the knifefish is an electrogenic species of fish, so I'm thinking it has something to do with that, I just don't know what to do exactly.
<Xenomystus nigri may detect electric fields created by its prey, but it doesn't use electricity to navigate (and is therefore different to the South American Knifefishes).>
Do I need to do a water change, or is it something to do with the acidity of the water?
<This species should be happy at normal water chemistry conditions, pH 6.5-7.5, 5-15 degrees dH. Apart from avoiding extremes, it isn't a fussy species.>
And if I do need to test the water, where could I go to purchase the proper testing instruments?
<You should have, at minimum, a pH test kit and a nitrite (with an "I", not nitrate with an "a") test kit. Although pH itself isn't everything in terms of water chemistry, it's a good "quick and dirty" way to check water chemistry. As for nitrite, that's the handiest test kit to check water quality. Any pet shop should sell these. Both liquid tests and dip strip tests can work fine, so get whichever you like.>
Thank you very much for your time. Your website has been a Godsend for me.
<Cheers, Neale.>

New African Knife fish not eating/RMF  10/4/09
<Hi there>
Two days ago I purchased an African Knife fish after researching for quite some time and visiting pet stores.
<Xenomystus nigri... one of my fave fishes>
I purchased a 55 gallon aquarium setup and cycled it for ten days,
<This is a quick cycle>
took a water sample to be tested, and finally purchased my knife fish. It is quite healthy (busy at night and still in the day.) It has plenty of hiding places, but does not seem the slightest bit inclined to eat. So far
I have offered him frozen bloodworms, earthworms, and tropical flakes at night when he becomes active. He is about five inches and very healthy. I have searched the web diligently, finding only similar instances where refusing to eat was a problem and have read that larger knife fish can be difficult feeders. I was hoping for some suggestions on how to get him interested in feeding, because I would really hate to lose the fish I was soo keen on keeping.
<Mmm, well... am not sure this system is fully cycled, nor the fish all the way settled in...>
Thank you,
<Do try some form (frozen/defrosted, freeze-dried (stuck to the side low against the inside viewing panel/glass) or live Tubificid worms to get this fish started on captive foods... And do search again on the Net using the scientific name. Bob Fenner>

New African Knife fish not eating/Neale  10/4/09
Two days ago I purchased an African Knife fish after researching for quite some time and visiting pet stores. I purchased a 55 gallon aquarium setup and cycled it for ten days, took a water sample to be tested, and finally purchased my knife fish. It is quite healthy (busy at night and still in the day.) It has plenty of hiding places, but does not seem the slightest bit inclined to eat.
<He will... just give it time.>
So far I have offered him frozen bloodworms, earthworms, and tropical flakes at night when he becomes active.
<Flakes are a bit of a non-runner to be honest. But earthworms should work.
Make sure they're of adequate size, and of course, since these are nocturnal fish, offer them at night, with the tank lights out. Wet-frozen bloodworms will be taken too.>
He is about five inches and very healthy. I have searched the web diligently, finding only similar instances where refusing to eat was a problem and have read that larger knife fish can be difficult feeders.
<Xenomystus are not usually fussy, and provided water quality is good, he should eat. It normally takes longer than 10 days for a tank to cycle, so I'm suspicious of that. How did you cycle the tank? What source of ammonia did you use? Simply running the tank without fish has no cycling effect at all. You must provide ammonia for bacteria to use, otherwise the filter can't mature. The usual options are to either add small doses of household ammonia, or else to add flake food every day to the aquarium (as the flake rots, it produces ammonia, and that feeds the bacteria). Either way, it is normally 7-10 days for the ammonia to spike and start leveling off, but a good three weeks before the nitrite levels spike and drop down to zero. Use a nitrite test kit, check the nitrite level, and if it isn't zero, that's the problem.>
I was hoping for some suggestions on how to get him interested in feeding, because I would really hate to loose the fish I was soo keen on keeping.
Thank you,
<Cheers, Neale.>

Re: New African Knife fish not eating  10/5/09
Thank you so much for responding,
<My pleasure.>
To cycle my tank, I used AquaSafe for the heavy metals and in the next ten days I fed the tank with tropical flakes.
<Well, adding the flakes should work. But I'd be staggered if it only took 10 days to cycle the tank. Three to six weeks is normal. My gut feeling is your aquarium isn't cycled, and until the ammonia and nitrite levels hit zero, you'll have some problems. Non-zero levels of ammonia and nitrite stress fish, and among other things, put them off their food.>
I had a sample of the water tested for nitrates and the man that showed me how, explained that it was at zero.
<Nitrate -- with an "a" -- is largely irrelevant here. Unless you have very high levels, freshwater fish generally don't care about nitrate levels.
It's nitrite -- with an "i" -- that matters, and above zero, this most certainly is toxic to fish.>
I will try Tubifex tonight, and hopefully he will give in.
<Would actually buy a nitrite test kit first, and check the nitrite level.>
Thank you soo much for your help!-Stephanie
<Cheers, Neale.>
Re: New African Knife fish not eating  10/5/09

Thank you for responding! I cycled the tank using AquaSafe and feeding it for ten days like there were fish in it and when I had my sample tested, the nitrates read zero,
<... actually, NO3 should be accumulating if the system is cycling...>
but perhaps he is just not quite settled in yet. I have bought some Tubifex worms and I will give these a try tonight. Thank you soo much for your help!
<Do read on WWM re biofiltration, cycling. BobF>

Re: New African Knife fish not eating  10/5/09
I took your advice and bought a good test kit, and determined the following: Nitrites are reading 0, Nitrates are 80-160, hardness is 25 (very soft), chlorine is 0, Total Alkalinity is 180-300, and pH is about 7.4-8.4 (Alkaline).
<Mostly sounds within the tolerances of this species. That said, the pH between 7.4 and 8.4 covers a lot of ground: an increase of 1.0 on the pH scale corresponds to a ten-fold increase in acidity or alkalinity. I'm
assuming this test kit is one with strips: while easy to use and certainly inexpensive, they are notoriously difficult to read and consequently can be unreliable. In any case, if you can have the pet shop confirm with a liquid test kit what the carbonate hardness (alkalinity) might be, and what the pH actually is, then that would be very useful.>
Since Nitrites are zero, should I not be concerned about the water quality?
<I'm still skeptical that you were able to complete the cycle in ten days... that's really a very short period of time (unless of course you added mature filter media from another aquarium). So I'd be sensitive to
the idea nitrite and ammonia levels might not be as low as you think. Try a test 2-3 times in one day; once first thing in the morning, another immediately after feeding, and then another a couple of hours thereafter.
If these are still zero, then yes, you are probably fine.>
Will this water quality contribute to the knife fish's lack of appetite?
<I'd try and pin down the pH. Xenomystus will do fine at pH 7.5, and should remain healthy even as high as pH 8. But above pH 8, and certainly at pH 8.4, it is out of its comfort zone.>
Thank you again for helping me!
<My pleasure.>
<Cheers, Neale.>
<<I think Neale (or I) mis-read the Nitrate reading... 80-160 ppm is WAY too high. Please read here re importance and reducing: http://wetwebmedia.com/FWSubWebIndex/fwnitrates.htm
and the linked files above. Bob Fenner>> 

Re: New African Knife fish not eating: MORE... & FW NO3 f'  - 10/05/2009
<<I think Neale (or I) mis-read the Nitrate reading... 80-160 ppm is WAY too high. Please read here re importance and reducing:
and the linked files above. Bob Fenner>>
<Bob, you are quite right. I missed that: in fact I've never even heard of nitrate levels that high. Stephanie, you need to do a big water change today, and another tomorrow, I'd say 50% each time. Did you do water
changes while cycling the tank? You need to, otherwise the nitrate just builds up. Don't feed the fish. Review carefully before you start feeding how much you're adding. With luck, once the nitrate drops to below 50 mg/l, and preferably below 20 mg/l, you'll find the Xenomystus behaves much more normally. Feed, sparingly, small morsels of food. Initially at least, maybe one earthworm, every other night. Cheers, Neale.>
Re: New African Knife fish not eating: MORE... & FW NO3 f' - 10/05/2009

Oh, wow, I am on my way to doing a water change, but before I did, just out of curiosity, I tested the tap water and noticed that the Nitrates are equally high coming out of the tap! I have a Culligan water filter and I tested it as well with absolute opposite results... Should I consider using the filtered water instead? There were no nitrates present at all, the water was a bit softer and not as alkaline. The Xenomystus at an earthworm last night, so he is giving in, but I feel the water is still stressing him. Thank you again!
<... Please read where you were referred to. I would NOT drink this water until it is tested by a professional. I would NOT use salt-recharged filter water... ALL this is gone over on WWM. Bob Fenner>
Re: New African Knife fish not eating: MORE... & FW NO3 f' - 10/05/2009

<... Please read where you were referred to. I would NOT drink this water until it is tested by a professional. I would NOT use salt-recharged filter water... ALL this is gone over on WWM. Bob Fenner>
<<Within the EU at least, the upper level of nitrate that is considered safe to drink is 50 mg/l; above that, your water supplier is *obliged by law* to act. It sounds as if your water is contaminated, e.g., by
agricultural run-off (the source of ~70% nitrate in UK water supplies, at least). As Bob says, this should NOT be treated as drinking water. Babies in particular are at particular risk (see "Blue Baby Syndrome"). Call your water supplier, now. Cheers, Neale.>> 
>A note here... Neale and I are certainly NOT trying to scare ("terrorize") anyone, nor are we "certified" health authorities of any sort... We are only trying to urge readers on to further awareness and possible action, to safeguard their livestock and safety. RMF<
Re: New African Knife fish not eating: MORE... & FW NO3 f' - 10/06/2009

Wow, I certainly will have to get someone to come out and check the water (we have a well and live near some farm fields...)
I went ahead and used reverse osmosis filtered water for my 50% water change (I would not dream of using the same tap water,) and the nitrate level is in the 30's! I may have to supplement the water with minerals, but at least this is bearable for now. Hopefully my problem is solved.
<One problem solved, and another created. Plain deionised water has zero buffering capacity and isn't suitable for fishkeeping (indeed, pure water is potentially harmful to fish). To each bucket of deionised water, add appropriate minerals to harden it up. You can buy ready made hardening salts (often called Rift Valley cichlid salts, as opposed to tonic salt or aquarium salt, which don't want). Or else, you can make your own. See here:
There's a recipe for Rift Valley cichlid salts, but use one-quarter to one-half the amount listed, since you want soft to moderately hard water for these fish; pH 7-7.5, 10-15 degrees dH would be ideal.>
Thanks again Neale!
<My pleasure.>
<Cheers, Neale.>

African Knifefish trouble 7/19/09
I have a 55 gallon tank well planted with silk plants, driftwood and fake rocks for hiding places, all of my levels are doing great and my water temp, is 79.4 F. I have a private well, so since my water is not chlorinated I do not use any chemicals in any of my tanks other than 1 TBSP aquarium salt per 10 gallons.
<Why are you adding aquarium salt? Most freshwater fish don't appreciate this. It's "old school" fishkeeping, back from the days before proper filters and so on. So unless you're keeping fish that need brackish water, don't add salt.>
I have had this aquarium for about one year. I have a couple dwarf gouramis, a gold Gourami, a couple small Bala sharks, 2 rainbow sharks, a red-tail shark, 2 Plecos, and a handful of assorted Corydoras.
<Well, none of these need salty water! What they want is something between pH 6 to 8, 5-20 degrees dH. Provided your well water falls somewhere in that range, and the water chemistry is reasonably stable, salt is redundant.>
I recently added a African Knifefish (Xenomystus nigri). I had never seen this fish before and fell in love with him immediately.
<Hmm... a nice fish in many ways, but predatory, and rather big when full grown.>
I had no trouble with him at all; I feed an assortment of flake, bottom-feeder shrimp pellets and I feed a mixture of brine shrimp and bloodworms at night, right before I shut the lights off. I loved him so much I went out and bought two more three days after I bought the first one ( I know now, from reading your site that that is WAY to crowded for three knife fish).
<They're only gregarious when young; adults are somewhat territorial, so it isn't smart to overcrowd them, and there's certainly no need to keep more than one unless you want to (and have the space).>
That was 2 days ago. As of last night all three were fine; they ate well and were very active last night and yesterday during the day, I read on your site that these fish like to hide and are shy but mine were always out in the open, and they were vey beautiful.
<Good! Shyness often depends on the aquarium: if there's shade and the tankmates are peaceful, even shy fish can be outgoing.>
This afternoon when I left my house all three were fine; when I came home all three were dying, and now, at 3:51 am they have all perished.
<Oh dear! Did you do a water chemistry or water quality test?>
I have three tanks and all of my fish are healthy. I buy all of my fish at the same store and have never had any problems with disease. I had all of the same fish for years and didn't have to buy any at all but I have been changing tanks around recently and gave my son one of my 40 gallon tanks to take to his dad's and I sent a bunch of fish with it, so I have been slowly increasing my livestock. After reading your site I suspect the reason my fish died is because of aquarium salt?
<Certainly won't be helping, but at the dose you're using, can't see that it would harm your fish.>
I cannot think of any reason for these fish to have died other that that.
I change >50 water weekly and use activated carbon power filter that cycles 500 gal/hour.
<The filter turnover rate is good, and while carbon is pretty useless, provided most of the filter is given over the biological filter media, this filter should keep the water nice and clean. Now, changing more than 50% of the water at a time is dangerous, unless you're very sure water chemistry remains constant. Exposing fish to sudden changes in pH, hardness, and even temperature can cause problems. You also don't use dechlorinator, and while your well water might not have chlorine in it, there may be other things, like copper from the pipes, that could be causing problems.>
I just don't know what I did to cause the demise of these fish and I feel horrible!. I would like to get another African Knifefish but not until I know what killed these ones.
<Knifefish are generally quite hardy, but they are intolerant of copper (including copper-based medications) and do require fairly good water quality at all times; 0 ammonia, 0 nitrite; and pH and hardness levels stably within the range mentioned above. Don't use water from a domestic water softener, either!>
Please Help!!
<Would need some data on water quality (at least, nitrite) and water
chemistry (at least, pH) before I could hazard a guess.>
<Very difficult to know what happened here. Would review environmental conditions, ensure that there's nothing stressful in the system (salt, copper, etc.), and wait a week or two to make sure the tank otherwise remained happy. If things looked good by then, and the pet store hadn't lost any fish, you might gamble on another specimen and see how it goes; you could always add a couple more down the line. Cheers, Neale.>

African Knifefish Problem.. it died. - 7/2/08 Hello, Recently I had bought two more fish to add to my 75 gallon tank; a Senegal Bichir and an African Knifefish, a Domino Synodontis and another Senegal Bichir were already in the tank. The first night the African Knifefish was added I had noticed a white spot on his side that looked almost like a bite. <Likely what it was. Whilst the fish listed here can work acceptable in robust community tanks, both Polypterus and Xenomystus have the potential to be aggressively predatory, particularly if they are hungry. Neither has good eyesight, and both hunt primarily by smell and using their lateral line. Or put another way, they sometimes bite whatever comes in range!> The Bichirs I have are very calm and peaceful and didn't mind the Knifefish, actually when we got them from That Fish Place they were in the same tank together. The catfish rarely comes out of his hiding spot and never bothers any of the other fish, so I do not know how he would have gotten a bite. <Synodontis do tend to avoid being bothered by other fish. For one thing they are quite heavily armoured (and armed). Synodontis also have a few behavioural features that help. They are, as you note, very retiring. They also tend to attack things that annoy them. Finally, they make "clicking" sounds that disturb other fish, and seem to work as quite a useful anti-predation mechanism (in Africa, Synodontis are known as Squeakers).> Over the next day that spot had gotten larger, it didn't even seem to bother him though. He was eating and very active. That night the spot had spread to an off-black color and began to stretch across the other side of his body. <When wounds get larger, even if they don't seem to "bother" the fish, you need to do two things: [a] establish the cause; and [b] treat preemptively for Finrot and Fungus.> I did a 20% water change and set the temperature to 80 degrees. Yesterday he seemed to be doing fine, even the spot looked like it was shrinking. This morning when I turned on the light he was on the bottom of the tank upside down. I'm just wondering what could have happened to my Knifefish. <Quite likely a secondary infection, perhaps exacerbated by stress or starvation, depending on how well settled and how well fed the fish might have been. Juvenile Xenomystus are somewhat gregarious, and the singleton might have been bullied by the Polypterus senegalus. That said, P. senegalus is generally very well behaved, particularly when compared to other members of its genus, so to be honest I'd be surprised if this combination of species didn't work in a tank of decent size and adequate numbers of hiding places. I'd review water quality and water chemistry simply as a matter of course; whilst Polypterus and to some extend Synodontis are "hardy" in the sense of being easy to keep, Xenomystus (like other Knifefish) are FAR from hardy in aquaria, and can be killed by ammonia/nitrite, rapid pH changes, many fish medications such as those containing copper and formalin. So there's a range of things to review there.> Any information at all would be wonderful, thanks. -Carly <Cheers, Neale.>

African Knifefish with Elephant Nose... Ost. comp.     01/13/2008 I've read conflicting information in various media concerning putting African Knifefish with Elephant Nose fish. <Indeed?> I'm moving my 7" African Knife into his own 55 gal tomorrow and would like to know if I can put my two 5" Elephant Nose with him. <Possibly, but Elephantnoses do get a bit territorial, so make sure it has lots of hiding places. Xenomystus nigri isn't one of the Knifefishes that generates an electric field, but it is apparently sensitive to them. So while I doubt the Elephantnose will make a bee-line for the Knifefishes in the same way it does other electrogenic fishes, the Knifefishes might get annoyed by the electric field from the Elephantnose, and that could lead to tensions.> I know both fish have weak electrical fields. <Xenomystus nigri does not generate an electric field. Appearances aside, it belongs to the non-electrogenic Notopteridae Knifefishes, a different group to the electrogenic Gymnarchidae and Gymnotiformes, both of which contain true electrogenic species.> Several sources say you can mix Elephant Nose with African Knifefish but *not to mix them with Black Ghost Knifefish. A bit confusing because they don't say WHY. Temperament perhaps? <Black Ghosts -- Apteronotus albifrons -- are members of the electrogenic Gymnotiformes group, and likely when Elephantnoses and Gymnotiformes are mixed, the two varieties of fish annoy each other with their electric fields.> The 2 Elephant Nose bump into each other but I've not seen any aggressive behavior in the 2 months I've had them, they seem to get along well and were bought together from the same tank. <In theory, Elephantnoses are schooling fish, but in captivity they often don't get along. The reasons aren't clear for this.> All 3 fish are great eaters but I'd like to keep them separate from my other fish because I'm afraid they just wouldn't be able to compete for food in other tanks. <Agreed, though provided Elephantnoses are mixed with species that never take food from the bottom of the tank, they can be placed in communities. Hatchetfish, halfbeaks, Danios, African Butterflies and so on would work.> Would it be a reasonable solution to put them together? There will also be a 1 1/2" Raphael Catfish but no other fish. <Certainly worth a shot. I tend to recommend against mixing catfish/loaches and Elephantnoses because of problems with feeding. But if your fish are feeding well already, then maybe you'll be fine.> Thank you for your time, options & your dedication. Sincerely, Mitzi <No problems, and happy to help. Neale.>

Re: African Knifefish with Elephant Nose  01/14/2008 I'm going to go look (online 1st) for "The Diversity Of Fishes" and snatch up the 1st copy I find, thank you! You can't put a price on a good book that you can refer back to for many years, I love books. It fascinates me that if we give a fish what IT needs (physically, psychologically & diet-wise) that the other aspects fall together. <Hi Mitzi. Yes indeed... one of the nice things about keeping fish (compared with, say, dogs) is that it's relatively easy to create an environment so natural the fish will complete its entire, natural life cycle in captivity including social interactions, courtship, breeding, and brood care. Dogs, by contrast, are largely limited to being pets, and rarely get to interact fully with other dogs, let alone organise themselves socially.> Common sense should tell someone Elephantnose don't need any bottom feeding completion. The fish shop told me to put them with Loaches and feed only brine shrimp, I just roll my eyes at them most the time. <All too common. Most stores see them as oddball "scavengers", which they're SO NOT!> These 2 will eat just about anything. I had to get creative but I figured out that if I cut stringy chunks of any kind of meat or insect they'll devour it. <Try putting in a small ball made of aluminum foil; supposedly Elephantnoses find these "toys" fascinating!> All my tanks have zucchini or squash in them and they even mash their funny noses into that. I haven't figured out if they're eating or not yet-but it's sure fun to watch them! <Not sure if they're eating it, but perhaps. They do hunt mostly by olfaction, and only secondarily using electric field detection. Hence they "touch" interesting things with that chin barbel to taste it.> It makes me wonder if they can communicate somehow. <Yes. Communication in Elephantnoses has been much studied and is known to be extremely complex. Essentially, dominant individuals "monopolise" the best frequency, and lower status individuals have to use less desirable frequencies. Within the group, there's constant jockeying as fish try to use the best frequency (i.e., the one that offers best navigation resolution). Presumably, they also use electric signals to convey things like sex and willingness to mate.> One will find food and 1/2 a second later the other one will come shooting as fast as he can from the other end of the tank. Just like chickens. <Hah!> I can't wait to find that book-thank you so much! Mitzi <There's quite a big chapter on electricity in fishes; it is a unique sense that fish have but no other vertebrate (something to remind those annoying "warm, fluffy animal" chauvinists! Enjoy, Neale.>

Re: African Knifefish with Elephant Nose  01/14/2008 Food for thought here. There was much you told me that I honestly didn't know. I don't know where else I'd have found such specific information (which is why I pick your brain often). I wish I had access to some sort of a "fish library" like the medical library we have. I'd be in heaven. <Hi Mitzi. If there's one book I'd recommend for anyone interested in fish beyond merely keeping them alive in a glass box, that book would be 'The Diversity of Fishes' but Helfman et al. It's a university-level text book, but so well written, and with so many diagrams and photos, that I think anyone with even a mild interest in how fish work and what they do will find it a fascinating read. Not a cheap book (I think I spent about £50 on my copy ten years ago) but should be accessible through libraries or used book stores if you don't want to pony up for the new edition. But trust me, once you've taken a peak, you'll want your own copy... it's that good!> I did move the African Knifefish & his little Raphael Catfish yesterday as planned but did *not put the 2 Elephant Nose in there, it didn't feel right to do so because the Elephant Nose are such busy bodies. <Elephantnoses are exceptional fish in many ways, and great fun once you understand their needs. They are among the very few fish for which scientifically accepted "play behaviour" has ever been observed, implying a level of intelligence well above what we normally associate with fish.> I didn't want Wendell the Knifefish to be stressed with all that activity. After reading what you had to say I'm glad I held off. <Cool.> The Elephant Nose have been in a 3 ft tank with 10 Hatchets and I guess they'll stay there until the aquarium fairy brings me a bigger tank for them. <Sounds as if he's happy. You seem to have figured out that Elephantnoses do best with surface-dwellers. Good call.> Thank you, Neale. You've no idea how much I appreciate you. <Not a problem.> Mitzi <Cheers, Neale.>

Re: African Knifefish with Elephant Nose  01/14/2008 So much I didn't know about the Elephantnose-even after all I thought I'd read. <Always the way!> I found the book and ordered it on Amazon.com. I'm so excited :-)) My birthday is Jan 15th so it's a birthday present to myself, I can't wait to get it! <Hope you will enjoy.> I actually do understand the interactions of dogs, to a certain extent anyway as mine are all spayed or neutered. Dogs were my "1st love" as far back as I remember. People seldom understand why I 'want' a dozen dogs in the house but then they don't understand my fascination with a dozen aquariums either. I see & understand the interactions between the dogs, I can tell at a glance what each dog is portraying to another, why they're doing it and how to either stop or encourage the behavior. The dogs know the 'leader' is the short blonde lady with the aquarium hose-ha! <You "get it" -- Dogs are happier when kept in groups of their own kind, not just with people. At the very least, it's so much nicer for a dog when you take it on walks with someone else's dogs too, so that they can make a little "pack" and go do their thing, instead of always following the Two Legs about.> Sorry to take up your time, but I learn so much from you and maybe what you write will help someone else with these same kind of fish. <Who knows!> Thank you!! Mitzi PS I'll try the aluminum foil with the Elephantnoses. It'll give me and the Hatchet fish both something to watch :-) <Let me know what happens. Have read this, but never seen it. Cheers, Neale.>

African Knife Problem and other questions  12/28/07 Hello, I work at fish store and learn new stuff everyday via online and book research. <Ahh!> However there are a few questions that I have for you gurus that I can't find the answers to. First, I am cycling my 65 gallon tank and it has been running for 6 weeks (weekly 25% water changes) with 3 Gouramis and two Cory cats and a new system dosage of Cycle. <Mmm, this Hagen product only seems to work... "some of the time". Marineland's BioSpira is far superior> There has not been an ammonia spike yet and I am wondering if it may have been small and I missed it or if I didn't get enough fishy waste to correctly cycle the tank? <Can easily happen... in a tank this size, this much time going by... it likely has> Next question: I want to buy this African Knife for the tank once it is ready but the Knife we have at the store has a strange white dot in the center of both eyes. It doesn't look like any cloudy eye I have seen but it wasn't there when he first came in. He appears to be able to see so I don't want to treat him if he is fine as Knifes are sensitive to medication. Any idea? <I would ignore this/the spot... likely a demelanized area consequent with a physical injury (a "jump"). Not treatable per se> Last question: I know that peace lily's are not submersible plants (they die after 6 months) but if you know this and take them out when their underwater life is nearing it's end, can you avoid a nitrate spike? <Yes... have seen this> I was told I could do this in my tank which is not appropriate for real aquatic plants, but it sounded a little fishy, no pun intended. Thank you for your insight. Julie <Thank you for sharing. Bob Fenner, who "spent" most of his youth in petfish retail settings>

Knife Fan Challenge, comp.  12/19/07 Thank you for your help in setting up our tanks (5, 48 and 75 gallons.) Due to Mr. Fenner's enthusiasm, I am now a Knife fish fan. I am now wanting to set up our final and largest, but before I did that, I wanted to double-check that I'm not headed for disaster. And as a side comment, it is frustrating with so much information on the web there are often conflicting opinions. For example, I thought my African Brown Knives (not Asian) would not be compatible in a pair, but after 6 months they co-existed peacefully, alongside one Black Ghost Knife who is now the same size as them at 8 inches! After finding a photo on the internet of a man holding a baby Black Ghost Knife in his hand that was born in his tank, I want to see if my Knives will breed as well, or at least, co-exist peacefully. I know this is an unusual undertaking, that is why I wanted to check with you, the supreme experts, first. If I were to get a tank of 125 gallons, then 3 African Brown Knives (24 inches of fish) with 3 Black Ghost Knives (45 inches total) would be 69 inches of fish (using the old rubric of one inch per gallon.) I also have had one Bala with the knives who has been happy and health and is now 9 inches (will get 12 I read.) I have also had 2 rubber-nose dwarf Plecos, 2 pictus Pim catfish and a Featherfin catfish, apple mystery snails and a three-striped Corydoras. Will or can these peacefully co-exist as the ghost knife fish become larger? <In this size system, likely so> So far all have been fine on a blood worm diet, weekly 50% water changes and vacuuming and testing the water weekly. The three knife fish have done well, but after I add the three more, and as the Black Knife fish grow larger, can I expect them (or the Bala) to eat the dwarf Plecos, pictus, the Corydoras or the snails? <No. They should be fine together> Then, if I may also ask, for the 75 gallons now that the tank is ready with perfect water conditions, do you approve of our adoption plan: Glass Fish, three-striped Corydoras, Round Glass Fish, Clown Plecos (4 inch dwarves), rubber-mouthed dwarf Plecos, one male Beta, guppies, silver Hatchetfish (2.5 inches) or marble Hatchetfish (1.5 inches) and either a Featherfin catfish or Bugeye Synodontis catfish. How does it sound? <This mix for your 75 should work... I would go with the smaller Synodontis species. Bob Fenner>

African knife fish (Xenomystus nigri) fish/system compatibility question  8/4/07 <Hi Matt, Pufferpunk here> I have read much of your site (actually just about everything in your freshwater fish section and half of the planted aquarium section) in my leisure time at work and I could not find a definitive answer to my query. <I wish I had that much leisure time at work!> I currently have a 120 gallon tank with seven 4-5" silver dollars, an 18" common Pleco and 6-8 Cory catfish (plus about 200 plus snails of various species). The tank is well established, (ammonia 0, nitrites 0, nitrates... too high, I wont be getting the knifefish unless I can controllably get my nitrates to under 20ppm) has a variety of floating plants such as Anacharis, Water sprite, and duckweed (which my silver dollars regularly nibble) and there is a large piece of driftwood which keeps the tank at a steady 6.6 - 6.8 pH. <I would suggest huge weekly water changes but I think that may cause the pH to fluctuate too much. Maybe a large sump/veggie filter is in order here. Definitely no adding of new inhabitants now.> I have built a PVC pipe condo with 2 inch diameter pipes that are 12 inches long each, into a pyramid type structure consisting of 15 tubes held together by Gorilla glue. I would like to buy between 5 and 7 African knifes to put in here. I have had one before (a while back in a different smaller tank) which only ate frozen food and instantly spit out flake food when tasted. I have read that these knife fish are somewhat sociable, not to the point of schooling but in that they do hang out together and when being fed dry foods, they would be more likely to consume it due to competition. Is this a sound theory that is tried and true? <I'm not sure where you got that info. According to Baensch: "Difficult, larger animals are solitary and aggressive towards other Xenomystus nigri". In other words, 1 per tank. I also think topping out at nearly 1 foot, you are dreaming of way too many knives in your tank.> Is it fish dependant? Or will it just take some time to wean them off but in the end, most should be used to flake food? (with the bi weekly frozen food treat of course). <Although fed a variety of foods (my knife lives with 7 discus) I have never seen my knife move from his hiding spot to eat anything on there than live worms. Although I read the fish can get used to strips of raw meat.> And also, is the size of my tank large enough for such a mixture? <I'd say that one of this species would work well with your set up.> Right now, the silver dollars mostly stay at the middle level and the Corys are also at the bottom and never in the PVC pipe condo, so I figured that maybe this would be suitable. My last question being, will the knife fish get along when they get older or will they become antagonistic like other knife fish? <No> I just bought a new light which has moonlight LED's so now I can actually observe the knife fish swimming around without sitting in the dark and holding a small flashlight on the tank, so I am rather excited for this purchase. <Cool!> The only things holding me back are my high nitrates (about 120ppm +/- 40ppm) and fish compatibility. <That IS high!> I only hope that my new aquatic plants (with their new 260watt full spectrum fluorescents and actinic bulbs, as opposed to the old 60 watt mercury bulb) and removal of my giant canister filter (Fluval FX5 aka nitrate factory) will be enough to reduce the nitrates in the coming weeks. Thank you very much for your help and for having such a detailed site. I myself work as a chemist in a machine coolant company so I often read many things which actually pertain to my job, which is always a plus. Thanks again. <Look into a large veggie filter for that tank. http://www.thekrib.com/Filters/plant.html#8 Please note that when purchasing, most of these fish that are bought as juveniles do not survive the first month. Enjoy your knife! ~PP> Matt, NJ

African Brown Knifefish. Electrogenic fishes, comp.    1/30/07 Hi! About 2 years ago I purchased an African Brown Knifefish <... is this an Apteronotus species? S. American? Or Xenomystus? Or?> and an Elephantnose fish (Fishie and Ellie, respectively). 3 months ago I had to go out of town, so my sister took care of my fish for me. Kind of. <Oh oh> When I got back I discovered the water quality was awful. I managed to fix the water, but Ellie still passed away. I want to get another elephant nose but I've since read that these 2 types of fish tend to hate each other. Is this true? <Mmm... depends on what species the former is... but in general, a qualified yes here... Electrogenic species of fishes are best not mixed in small volumes/aquariums> These two always would play together and even slept in the same little pot, despite have numerous places to sleep separately. Should I scratch the Elephantnose plan and just get a different type of fish? <Mmm, up to you... but I would be prepared to move the newcomer if there was obvious agonistic behavior> I'd be devastated if anything happened to Fishie. The tank is 55 gallons and is being upgraded to 95 in June, if this makes a difference. <Does... the larger the "world" the more likely they... and other species will get along> Thanks so much, Amanda <Thank you for sharing. Bob Fenner>

Freshwater tanks - African Knifefish question, cichlid in/comp.    12/28/06 Hi there. <<Hi, Stacy. Tom here.>> Can I put a Black African Knife Fish in with a couple of African Cichlids? Just starting a new tank and am not sure of this. <<It depends a great deal on the size of the tank that you're starting, Stacy. Less than a 50-60 gallon tank would be too small. These fish can grow to a foot in length. Factor in the size of the fish you want as tank mates as well. Compatibility-wise, they need to be with large fish since smaller fish might look like lunch. (Tank size again.) You'll need to provide cover, i.e. hiding places, for them since they're not particularly active during the day. Beyond this, your question is a bit difficult to answer without more information regarding what I've already mentioned and the species of Cichlids you'd like to house your Knifefish with.>> Please help.  Thank you. Stacy <<Your welcome even though its only a start. If this isn't enough to go on, you know where to find us. :) Happy Holidays to you. Tom>>

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>

Knifefish selection mostly  2/3/06 Sorry to be bugging you so much, but I just had a few more questions... my dad has agreed to buy me a 70 gallon tank in the near future (!!). I was just wondering what you meant when you said the Xenomystus nigri is a Notopterid. Does this mean it is a bad choice? <Oh no... just that it's not a member of a what folks typically consider (South American families of mildly electrogenic fishes> Also, when I do (if I do) get an elephant nose, does this mean they will be compatible (Is the African knife a Mormyrid)? <Not likely trouble... I would not mix electrogenic fishes... Notopterid (see the family... on WWM, fishbase.org) are not> I recently noticed that one of my small angels has sort of deformed gills. It breathes heavily and some of the gill is exposed on both sides, however it is feeding well and loves frozen bloodworms. anything special I should be doing for it? <No... likely a typical genetic-physical/developmental defect here> Lastly, do you know any good ways to get rid of unwanted fish? <Mmm... a large/r predatory animal that will eat the excess culls> Most of my local stores do not want them, except maybe for Petcetera. However, I do not feel comfortable giving my fish to them. Though the staff are more knowledgeable than those at, say, Wal-mart, they do not seem to care much for their fish once they are sold. Lately, I saw them carrying small Oscars, with no warning to how large they grow, as well as deceptively small piranhas (1-2 inches - for $25!!!!). They cannot even keep a tank of guppies alive, so I do not think they should be carrying these fish. Thank you for you advice, and I have talked to my parents. They agreed to let me volunteer/work at a pet store on weekends/holidays. Now all I need to do is find some place that will take me! -Eddy <Are there any fish clubs about in your area? You might find friends there to trade with... establish networks for such. Bob Fenner>

African Knife Fish With Bubbles  11/29/05 Hi. After reading many of your posts, I attempting to self-diagnose one of our fish. My husband has temporarily relocated for work, and I've been taking care of the tank. Have not done a partial water change in three months. Problem, the African Knife Fish has developed white spots on its body. Since most posts discussing Ich refer to it as flour-like spots, I'm not convinced that's what this is, although I'm close to being convinced. The spots look more like bubbles on its body. They actually look like little air bubbles attached to its skin. The water temperature has gotten low, 76 degrees, and I just returned from the pet store and they told me nitrates were "extremely" high. I purchased nitrate lowering granules and put them in immediately. I plan to do a water change. How much?  Also, most meds for ich use the Malachite Green and one of your postings indicated that is toxic for knifes. Was considering following advice you gave for: "Ghost Knife sick - please help" Still wondering if you think this might be a fungus? How do I tell for sure it's Itch, if it's not a fungus. Would like to save my husband's tank. Will quarantine the Knife if you think best. Help. Thanks. Kimberly < If you have a heater then make sure it is working and turn it up until the light comes on. Continue to do this for a couple of days until the water temp is up around 80 to 82 F. This heat will take care of any ich in about a week. I think the bubbles are really bubbles and are caused by bacteria growing on the skin. After the water is up to a proper temp then I would clean the filter thoroughly. After a long time it is not going to be a pretty job.  Do a 30% water change and replace the water with treated tap water. Any good water conditioner should work. Next week you should vacuum the gravel. Your local fish store should be able to sell you a gravel vacuum that will remove the junk caught in the pore space of the gravel. This will reduce the nitrates. As the nitrates go down the water will be better and the fish should be getting better too. Clean the filter once every two weeks. On the weeks you don't clean the filter I would do a 30% water change. Once the nitrates are reduced the bubbles should be almost gone. If not then treat with Nitrofuranace as per the directions on the package.-Chuck>

African Knifefish - 11/03/2004 I recently bought a brown knife fish. <Xenomystus nigri....  Usually called the African knife, sometimes sold as the brown knife.  Is this your fellah?  http://www.fishbase.org/Summary/SpeciesSummary.cfm?genusname=Xenomystus&speciesname=nigri  There *is* a fish more similar to the black ghost knife referred to as the brown ghost, but I've only seen this fish once or twice offered for sale.> (It's been about 10 years since my last aquatic impulse buy. I was due.) <Tsk tsk....  ;) > I put him in a 55 gallon  aquarium containing 5 hatchets, 7 harlequin Rasboras, 5 zebra Danios, <All of these may one day be food....> 1 sunset Gourami, and 3 Cory cats. He doesn't seem to be bothering any of them. He's  only about 4" long now. Brown knifes don't get as big as clowns, do they? <Hoo, goodness, no!  The clown gets over four feet long!  The African knife is, perhaps, the *only* regularly available knife suitable for your tank, topping out at about 12", and often a bit smaller than this.> Will  my tank be big enough if I don't add any more fish? <I believe so.> When he gets bigger, will my  other fish be in danger? <Plausibly.  I would try very hard not to be too attached to your smaller fishes, right now....> Since I don't get to see much of him, how do I know if  he's getting enough to eat? <Feed after lights-out on the tank.  Leave a small light on in the room the tank is in; just enough for you to see by.  After waiting an hour or so, sneak in with some stinky yummy treats (I've seen these relish frozen bloodworms like nothing before!) and wait until he finds it.  You can use a cone-type worm feeder.  If this doesn't get him biting, you might try live ghost shrimp or live Blackworms; the former is the "healthier", "safer" choice.> How do you feed live earthworms to them? <After lights-out, try holding the worm by hand so that some/most of it is in the water near the knife.  Wait.  See if he bites.  Don't fear, eventually this fish will be easier to feed, and will recognize you as the bringer of treats.> I know from past experience (with fire belly newts) that they try to burrow into the gravel before they get eaten. How do I keep the worm where the knife will find it? <Again, try by hand, or perhaps you could use a dish of some sort to place the worm in?> I really appreciate any advice you can give me. JoLynn <Good luck with this new knife....  One of my favorite oddities, by far!  Wishing you well,  -Sabrina>

Everybody To The Limit! - 04/13/2004 I purchased a knife clown about 5 days ago.  He's about 3 to 4 inches long.   <Aww, just a little baby!  Just to check, you do realize that these beauties get over four feet long, yes?> I have him in a 30 gallon tank with 2 gouramis, 2 tiger barbs, 2 angels, a large Pleco, a 4 inch silver dollar, a small Cory cat, a small tetra, and a Kuhlii loach.   <Uh, and a partridge in a pear tree??  This is, nicely put, a little much for a 30 gallon tank, I'm afraid.> I realize knife clowns grow rapidly and that I will not be able to keep this one in my tank for long.   <Or any tank....  A few hundreds of gallons would do for a couple of years.> However, I have fed him fish flakes, freeze dried plankton, freeze dried Tubifex worms, brine shrimp and feeder guppies, and he has exhibited little to no interest in any of these.  I have yet to see him eat, though he swims around freely during feeding time.   <Try frozen bloodworms, pieces of krill, squid, prawn/shrimp.... and skip the feeder guppies, unless you breed them yourself; they run a *terribly* high risk of giving your fish disease.> All the other fish chowed down.  I have also noticed that his fins are nipped.   <Uh, not to be cruel or anything, but what do you expect?  A thirty gallon tank is not suitable for the sheer volume of fish you've got, and *especially* not suitable for a knife capable of growing taller than your average school kid.> I have noticed the silver dollar nip at him a couple of times.   <I would not doubt it.  The barbs are undoubtedly to blame, too.> Any suggestions?   <First and foremost, I would forget about the knife for now.  I hate to be harsh, but there is just not a place in your tank for such a fish right now.  If the stress from the crowd doesn't kill him, the barbs and silver dollar will, I'm afraid.  Then I'd recommend focusing on how to hone down your bioload some; characins are schoolers, and need to be with others of their kind to thrive; you might consider doing a separate tank for the silver dollar, and get him a couple pals, and include the barbs in that tank, and the tetra with some friends, too.  That would take you down to two Gourami, two angels, a Pleco, a Cory, and a Kuhli in your 30g.  The Plec will be next to need a bigger home, if he doesn't already; you implied that you planned on moving the knife to a bigger tank - perhaps instead, you could upgrade, and move this batch (Gourami, angels, Plec, Cory Kuhli) into the bigger tank, leaving the characins in the 30g?  I'd add a couple more Corys and a couple more Kuhlis, too; they, too, are better in groups.  Then, after that's settled, you might like to consider Xenomystus nigri, the African Knifefish, for your larger tank.  This is really the only knife available in the trade that will not grow far too large for the average tank; they top out at about eight inches.  Here's Fishbase's rundown on 'em:  http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=5065&genusname=Xenomystus&speciesname=nigri .> I am at a loss for what to do next. <There is really nothing you can do to make the current mix work....  I do not foresee the knife surviving in the current scenario.  I hope that this has been of assistance to you....  Please forgive the "nagging"; I only have the interests of you and your fish in mind.> Thank you in advance, Mariella <Wishing you and your finny pals well,  -Sabrina>

Ghosts, Knives and something else I have a 55Gal tank with only an 8in. Black ghost <max over 12"> and a 7in. African black knife <max 8 to 12">. I am trying to find what other fish I can put in the tank and how many of each would be appropriate. I used to have a Silver Arowana but he got way too big for the tank (27in) so I had to find him a new home. And my albino clown that I loved died after I took the Arowana out. I have tried Nicaraguense, Bala sharks and a Green Terror but the cichlids seem to pick on the black ghost and the Balas are so twitchy.  I am thinking about trying another clown but it would be nice to have some fish they weren't always hiding. The tank is pretty lonely and I don't know who would be most compatible with the ghost. I don't want him to become fish food <Nothing that will fit in a 55 will take an 8" ghost> or make fish food out of them <Very likely, unless too large to fit in it's mouth>. Nicole. <The biggest problem I see is the size of your tank. A 55 is fine for what you have now. But you would have to add some fairly large fish to ensure they do not become a late night snack. And if you want a few of them, the 55 shrinks in my eyes. Clown loaches come to mind. They grow large, but slowly. Some of the larger Cory species would also be safe. Don>

African Brown Knifefish Prob... I have a 6 inch African Brown Knifefish that has a problem. Recently I noticed weird shaped blotches in its skin that look like scars and then it started rubbing itself against a rock in the tank and now it seems to be all cut up what can the problem be. Is it fish slime or some other fungus? Thanks for your help. <Take a look at http://www/wetwebmedia.com/FWSubWebIndex/fwfshparasites.htm for a list of common problems along with their recommended treatments. Ronni>
Re: African Brown Knifefish Problem...
Hi sorry to bother you again but with the descriptions on the page I could not identify the ailment so could you just list maybe a few of the best things I could do... some cure-alls or cure-mosts in this case.( my Knifefish is sick) Thank you so much. <The one thing to really check is your water quality. There really aren't any cure-alls that you can use if you don't know what the problem is. You need to do some research and see if you can pinpoint the exact problem before you start medicating. At the very least you will need to determine if its a bacterial or parasitic problem or something else. Try searching at http://www.wetwebmedia.com and also on the web for these symptoms. Look for specific African Knifefish pages too. Ronni>

SICK JACK THE KNIFE I have an African Knifefish and it is pretty hard to find useful information about this species. I have a 55 gallon tank that recently got ich as a result of a fairly new clown loach. The loach died and gave it to a Danio and another loach I had. I raised the temp to 85 degrees and I have raised the salinity to 1.003. (Over a period of a few days of course). The loach's spots went away as well as the Danios and I haven't found any other traces of ich.  Things have not been going well however. Yesterday, I found a dead African dwarf frog and today I found a heavily bloated Danio who is probably dead by the time you read this. My other Danio looks like his stomach is protruding a bit as well. I checked my knife and he has these two big patches of white. I didn't know if it was ich because it isn't small dots it is a very large patch (about 3cm) and another patch (about 1 cm).  I have two small Plecos that I haven't noticed any problems with and I really don't want anything to happen to my knife. Are the large patches ich or something else? They have just showed up today and were not there yesterday so I am catching it pretty early. Any suggestions? Thanks for any help and great site. < Your tank is breaking down from the water treatments. Drop the water temp to 78 to 80 degrees. The high water temps are stressing your Danios and causing the bloat. Do a 30% water change, and vacuum the gravel. Service the filter too. Check the ammonia and nitrite levels, they should be zero. Check the nitrates. They should be lower than 25 ppm. Now that the tank is cleaned up you need to treat those bacterial infections on the knife fish. Use Nitrofurazone and back off on the salt. This medication may affect the good bacteria that breaks down fish waste so watch for ammonia spikes.-Chuck>

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