FAQs on the Aba Aba, Upside Down,
Feather Back Knifefish
Related Articles: Gymnarchus niloticus, Knifefishes,
Related FAQs: Bony Tongue Fishes,
Arowanas, Featherfin Knives, Mormyrids, New World Knifefishes,
Aba aba knifefish; Trauma
Good morning, I had a accident with 2 fish that I had separated. In
preparation of transitioning my 20" Aba aba knife to its own tank, it
was in a divided tank opposite a single Caribe piranha.
Aba somehow ventured over the wall last night and was bitten pretty
badly on the back end. His entire tail, and an additional several inches
of body/flesh is gone. The Aba actually seems fine, and I have made
other arrangement for housing. How much should I expect to grow back?
<Hard to state (as I only have limited first and other hand... reading,
experience with this species). I will state that like many related
species, this one does have "remarkable powers of regeneration". And
that depending on how far forward the actual vertebrae, distal nerves
are gone, may mark the limit of regrowth. To summarize, one can only
keep up good conditions (water quality, nutrition) and hope for the best
Am sharing w/ Neale Monks here for his independent input. Bob Fenner>
<Thank you for sharing. Please send me/us follow-ups with your thought
processes, experiences. Bob Fenner>
Aba aba knifefish; injured. Neale's go
Good morning, I had a accident with 2 fish that I had separated. In
preparation of transitioning my 20" aba aba knife to its own tank, it
was in a divided tank opposite a single caribe piranha.
somehow ventured over the wall last night and was bitten pretty
badly on the back end.
His entire tail, and an additional several inches of body/flesh is gone.
The aba actually seems fine, and I have made other arrangement for
How much should I expect to grow back?
<Assuming excellent water conditions, frequent water changes (ideally
daily) until the flesh heals over, and immediate use of a good quality
antibiotic medication against Finrot, there's a good chance your fish
will survive. Whether it'll actually regrow its tail completely is
harder to say. Most likely it'll end up with a skin-covered stump of
re: Aba knifefish 7/2/17
aba knife fish; fdg. /RMF
I have recently purchased a aba aba knife fish of 15 inch and kept it
with my black Arowana in 3 ft tank on temporary bases
<Dangerous.... inappropriately small. MOVE ASAPractical to larger quarters>
and the fish is only eating live fish. Is there any way that I can change her
diet to dry shrimps.
<Perhaps mixing in some of the same sort/s of fish/es (dead) w/ the dried
shrimp... SEE/READ on WWM re Feeding Knifefishes of all kinds (the FAQs).
aba knife fish; fdg. /Neale
I have recently purchased a aba aba knife fish of 15 inch and kept it with my
black Arowana in 3 ft tank on temporary basis
<I'll say! aba (Gymnotus niloticus) get extremely large and are very
aggressive. Expect an adult length of over 1 metre. They are very territorial,
and usually vicious, biting anything else kept with them. An Arowana could
easily be killed by one, whether directly or by being so frightened the Arowana
and the fish is only eating live fish.
<Very bad idea. Do NOT do this. All you are doing is introducing parasites and
Is there any way that I can change her diet to dry shrimps.
<Dry shrimps would be only occasional treats. Shrimps (and prawns and other
crustaceans) contain Thiaminase. Over the long term this leads to a vitamin B1
deficiency, the cause of many problems with carnivorous fish. Do read here:
Many safe foods will be taken including tilapia fillet, earthworms, and cockles.
You may need to starve your aba for a few days, but
that isn't a problem. aba will take frozen foods without fuss, and some also take carnivore
pellets (such as Hikari Massivore).>
Gymnarchus niloticus with white eyes -
Amazing website - the wealth of information has certainly helped
so many of us to care for our fish better.
<Nice of you to say so.>
I purchased a young 14 cm Gymnarchus niloticus two months
<Still a baby.>
and it has been housed in a 180 litre tank with plenty of cover
and filtration. I know it grows to an enormous size and I'm
making preparations for a much larger tank for it.
<These fish are gigantic and notoriously aggressive. They are
not really suitable for home aquaria.>
However, it's eyes have recently turned white. Nitrites and
Nitrates are at a low but not completely zero, which I fear may
have been the cause of the disease.
<Correct. Chronically poor water quality will cause skin
infections, including damage to the cornea, which is the issue
here. But I suspect physical damage is the aggravating factor,
e.g., by throwing itself into the glass walls of the tank. Also
be aware that live feeder fish can introduce a variety of
parasites and infections, including Eye Fluke, so
should never, ever be used. Other possible causes include
exposure to chlorine (i.e., incorrect/no use of water
conditioner) and poor diet (specifically, vitamin A
I first thought it was a cotton wool-like fungus that grew over
its eyes, and I have added some medication for external fungal
<Unlikely to help without establishing the causes.>
But after a week of treatment, it has not shown signs of getting
After closer examination, it seems that the lens itself are
white, and thus I now suspect that it could be Cloudy Eye
Disease. I want to hear your opinion on it from the photos
attached before I treat with different medication.
<You really do need an antibiotic -- not an antibacterial --
and you also need to optimise water quality. Zero ammonia, zero
If it is cloudy eye, I understand that I will have to use
antibacterial medications. As Gymnarchus are similar to
Mormyrids, do you think I will need to lower the amount of
<Avoid malachite green, formalin and copper. Antibiotics and
Methylene blue should be fine.>
The fish is still eating and moving around well.
<And will likely lose its eyes, unfortunately.>
Thank you for your comments,
Re Gymnarchus niloticus with white eyes --
I am pleased to inform of you good news regarding the same fish
that I emailed you about two months ago. After heeding
Neale's helpful advice on care and medication, the baby
Gymnarchus niloticus has recovered fully after treatment and
It's been moved to a new, properly cycled 4ft tank for it to
live by itself.
<Cool. Will need more space eventually, as you
It's been a great joy seeing it recover and grow healthily,
excitedly begging to be hand-fed pieces of market prawns
<Do use these sparingly because of the thiaminase issue; would
use tilapia instead, if you can.>
and carnivore pellets every time the fishroom's lights are
turned on. I know how huge Gymnarchus can grow to, and thus I
have made plans for it to be moved to a large display tank at a
friend's place. Till then, my family and I will be enjoying
the care of this beautiful and surprisingly resilient fish.
<Certainly a fish with lots of character!>
<Do look out for the excellent 'Jurassic Fishes' book
from TFH. Been out of print for many years, but I suspect if you
can find a used copy online or in a second-hand bookstore,
you'll enjoy much of the content. Cheers, Neale.>
Gymnarchus niloticus, gen... & cramming
Loricariids, other madness 4/28/10
Thanks for such a wonderful site.
<Kind of you to say so.>
I'm picking up an Aba knifefish tomorrow that is very young and
small, about 4 inches, that I ordered from my LFS.
<I hope you know what you're getting yourself into here. These
fish are insanely aggressive and require huge tanks.>
I currently keep two freshwater tanks, a 135 gallon and small 10
<Neither of which is suitable for Gymnarchus niloticus.>
I know that the will require a massive tank by himself as he
<Understatement if ever there was one.>
but will he be ok in my 10 gallon as a baby?
I currently keep some small Plecos in the 10 gallon, a
"vampire" Pleco L007( 4"), an albino Bristlenose Longfin
Pleco (3" including his long fins), a royal Pleco (3"), and a
very small "snowball" Pleco (2").
<You are wildly overstocked already. Even if water quality is
acceptable now, it won't be for long, and the Royal Plec alone
needs a tank upwards of 55 gallons once it matures. As juveniles these
Plecs might be kept together
in a 30 or 40 gallon tank, but these catfish aren't necessarily
friendly fish, and Royal Plecs especially are notoriously intolerant of
other Suckermouth catfish, to the degree they can kill potential
Leporacanthicus cf. galaxias gets to about 25 cm, Baryancistrus L142 to
25 cm, Ancistrus to 12 cm or so, and Panaque nigrolineatus to well over
30 cm. Bear this numbers in mind, and choose aquaria
I also have two snails in there to help keep the bio load balanced.
<What? Snails don't "balance" anything, and pray tell
me what "bio load" might be. If the pet store told you adding
snails makes the tank cleaner, then they took you for a ride.>
It has worked well for about 6 months now and the tank is doing
<Not for much longer. After six months these catfish will have grown
appreciably, and really do need to be moved into a proper sized
My goal has been to raise some of these Plecs for my 135gal tank, but
only the L007 is near acceptable size for a transfer. The 135 gal has a
Ruby Oscar (12"), Green Scat (she's been in freshwater for 6
years now, 9"),
<NOT A FRESHWATER FISH!>
BGK (10"), Jardinei Arowana (12"),
<Do you have any idea how aggressive this fish will be when it
becomes sexually mature, which isn't far off.>
Jack Dempsey (7"), Common Pleco (15"), Orange Spot Plec
(8"), and a "chocolate albino" Pleco. Can I raise my
in this small tank for a little while?
Will he and the L007 clash? There's lots of hiding places, but am
thinking I may need to move the L007 to my 135gal, or just obtain a new
small tank to raise the in for now. Also as far as food goes, I was
Tubifex and frozen krill to start. Is that an acceptable well rounded
diet for this young knifefish?
<Least of your problems. Gymnarchus niloticus eats anything, and
provided you avoid fat and thiaminase, you'll be fine. Earthworms
are good treats for new specimens, but any fresh or wet-frozen fish
fillet and seafood should do.>
Thanks in advance for your help, you all are Godsends!
<Craig, you have some seriously insane ideas on mixing fish. I know
it's tempting to buy one of everything, but you really can't,
and just as you can "win" at Russian Roulette for a while,
that doesn't make Russian Roulette a safe game. Think very
carefully about what you're doing here, and what you're trying
to achieve. Some of these fish are among my personal favourites, so I
sense we share much in the way of taste. But there are limits to what
we can do when combining oddball fish in the same tank.
Read, reflect, and act accordingly. Cheers, Neale.>
Re: Gymnarchus niloticus -- 5/17/10
Thank you so much for the speedy reply. I'm a big fan and am humbly
following your advice :)
I decided to wait on the Aba and take care of my Green Spotted Scat
instead (Her name is Ruby because the LFS sold her to us as a Ruby
<Plain vanilla and ruby scats end up looking the same as adults
I REALLY want to raise an from juvenile to maturity one day, but
I've been meaning to switch Ruby to brackish water for quite some
time and obviously its very important.
I cycled a new 55 gallon aquarium and have Ruby in it now. I just found
a WWM article, authored by none other than yourself, that says she
should be slowly acclimated to SG 1.010, and to do water changes that
raise the SG by
no more than SG .002 at a time. How much of a water change should I do
each time? 25%? Also, what should the SG of my new water be to only
raise it .002 on each change for a 55 gallon?
<Oh boy, none of this is necessary for the fish. You can dump a scat
from freshwater into seawater and it'll be fine. But the problem is
with the filter bacteria. If you've cycled the new aquarium as a
freshwater tank, then yes, it's best to do small salinity changes
so the bacteria aren't shocked. So if this was me, I'd add the
Scat to the newly cycled freshwater aquarium, then do a 20% water
change that day with SG 1.003 water, and then another similar water
change the next weekend, and so on until the tank is SG 1.003. I'd
then do weekly 20% water changes with SG 1.005 water, and again, after
4-5 weeks of this, you should find the tank is at SG 1.005.
That's fine for a good long while, six months or more, but
eventually you can do a similar set of weekly water changes nudging the
salinity to SG 1.008, and then again to SG 1.010. Why such small
increments? Because the
freshwater filter bacteria have to die off and be replaced by saltwater
ones, which they do around 1.005, and if you rush, you'll end up
with the Scat in an uncycled aquarium.>
I have a bit of explaining to do on my choice of the Jardinei in my 135
gallon tank. I bought her when she was a juvenile and shortly after I
brought her home one of her eyes fell out! So she has one eye and was
raised in my 135 gallon "knowing her role" amongst the larger
fish. I do understand she reaches sexual maturity soon, and have been
keeping an eye on her, so to speak. There are plenty of hiding spaces
and territories for everybody. I also realize the Plecs in he 10 gallon
need to move as they grow, and am hoping to keep them in the 135 when
they start to get larger, and then on to their own species tank.
I'm a Plec fanatic!
<Join the club.>
Thank you for the info about the Royal Plec being aggressive. So far he
has kept to himself always, I've had him for about a year and a
half, but will keep this in mind when monitoring them.
<Does likely depend on the specimen. But if you spend a little time
on Google, you'll find some Panaque nigrolineatus horror
Again, thanks so much for all that you do in the aquaria community and
<Glad to help. Cheers, Neale.>
Re: lungfish and love! Gymnarchus
7/29/07 WOW! Thank you so very much for this information. I better
get right on building this "bullet proof" tank.. can't
abandon him now! :) Thanks again, you all provide an amazing website
packed with so much information, the most reliable as I can tell.. Love
and light Kimmy <Good luck, Kimmy. A lovely fish, a real treasure,
and one that will bring you many years of enjoyment. Cheers,
Aba Can you tell me everything you know about the
Gymnarchus niloticus? I need as much info as I can find about these
guys. Thank you <Please insert these names in the Google search tool
on our homepage: www.WetWebMedia.com Bob Fenner> Bruce
Query re Gymnarchus Could you give me any information on the Upside
down Knife fish (aba Gymnarchus), and possibly a guide
price? <Gymnarchus niloticus? Please look up on fishbase.org>
Could you include: length, water parameters, compatibilities, possible
size & age and any other information you can get. Thanks, <