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FAQs on Peacock Spiny Eels

Related Articles: Spiny Eels The truth about spiny eels; A closer look at these popular but problematic oddballs by Neale Monks, Husbandry of the Barred Spiny Eel, Macrognathus panacalus by Marco Lichtenberger, 

Related FAQs: Spiny Eel Identification, Spiny Eel Behavior, Spiny Eel Compatibility, Spiny Eel Selection, Spiny Eel Systems, Spiny Eel Feeding, Spiny Eel Disease, Spiny Eel Reproduction,


Peacock Eel, beh.; fdg.    8/22/18
I have a peacock Eel for roughly 8 months now. At first he hid all the time but now he is very active. Wondering if this is normal.
<Yes; this is normal behavior for spiny eels. Most are very shy initially, becoming more bold with acclimation, a dearth of bothersome tankmates>
I'm thinking he's hungry because he's out. And have been feeding him pretty much every day for the past 3 days and he comes to eat every time. Do I need to give him more at feeding times so he can go back to hiding. Or is he comfortable now?
<I gauge how fit fishes are as folks do in the fisheries industries; by apparent "girth" of the specimen. If it appears full, it is likely fine food-wise. Better by far not to over-feed; shortens life spans and presents
more maintenance>
Thank you much,
<Thank you for sharing. Bob Fenner>

Tough Decision to Make; Mormyrid comp.      6/14/17
Hello Crew! This is Renee from Idaho with yet another situation specific mormyrid question for you.
<Fire away.>
But first I have to tell you that my BGK is doing beautifully, staying healthy, growing, and continuing to enchant every day (getting the catfish for her was a brilliant idea! Not only are they keeping the tank clean, but she feels more comfortable with them than any other dither fish I've tried and now she moves around the entire tank - thank you again for that suggestion).
However, in the past I've shared with you my desire to get an elephant nose someday. I've put it off because that species is not available in my area and because I wanted to focus on my BGK and other tanks, but now I find
myself in a situation. My local aquarium store, who I previously asked about the availability of the elephant nose fish, gave my information (with my permission) to a military couple, who are being relocated, who have an elephant nose they can't take with them, but they only want to give the fish to someone with experience with Mormyrids.
I told them my experience was very limited (at best), but invited them out to see my tanks and talk with me about taking the fish. We had a nice visit and they loved my BGK (who chose to be very social for the occasion).
I explained to them that while I wanted their elephant nose, that I did not have time (or the energy) to properly prepare a whole other tank for the fish before they were going to be forced to leave (I have an empty 55 gallon, but it's dry, has no substrate, filter, or heater - I've just been storing it). Still, they seemed quite determined to get me to take the fish and suggested that it would be fine in my 75 gallon.
Well, my 75 gallon currently houses 2 rope fish, one peacock eel, and a 2 inch Bristlenose, and I just don't know if that group would be compatible for ALL the animals.
<Very difficult to predict. In terms of tank loading, not a problem assuming good filtration and regular water changes. The question is whether the Elephantnose and the Black Ghost will coexist. Ecologically, they occupy very similar niches so there will be competition for them in terms of swimming space, hiding place, food, and most importantly, electrical frequencies. This latter is the key here: if they jam one another, they'll irritate each other, and because the sense is electrical, not visual, you can't really "hide" them from one another by adding more rocks, plants, etc.>
I told them I believed the peacock eel also found its food by use of an electrical signal and I don't know if that would cause a problem for the elephant nose or the eel.
<I'm not aware of electric sense organs in Spiny Eels, but I could be wrong. If they have one, it'll be passive, like on sharks, simply able to pick up the electric signals caused by muscle contractions in prey animals; fish with active electric senses, like Black Ghosts and Elephantnoses, have distinctly "stiff" bodies so that the electromagnetic field is fixed, allowing them to sense the distortions caused by obstacles, rivals and prey. Much more sophisticated!>
I told them I wanted to help them, and that I wanted the elephant nose, but I wasn't going to sacrifice the current residents of my 75 gallon tank, the elephant nose, or my sanity by forcing this.
I've been researching since last night and can't find anything specific, both for or against, putting the elephant nose in with the rope fish and eel, so when they called me this morning, I told them I was going to write to you for your advice - if you thought it would work, I'd take the fish; if not, they were going to have to find someone else to take it. So, what do you think?
<I'd give it a shot *if* you had the option of returning the Elephantnose if they squabble. But if you're lucky, the two species will use different frequencies, and beyond territorial skirmishes, will ignore each other. I wouldn't bet the house on it, but it'd be worth a go, particularly if both specimens are still relatively small. Neither species is heavily armed, so aggression tends to be a slow burning sort of thing, with stand-offs and chases, rather than bites. So all else being equal, you can see if they're failing to get along, and act accordingly. Cheers, Neale.>
Re: Tough Decision to Make. Mormyrid comp.       6/15/17

I'm sorry, I should have been more clear. The elephant nose would not be going in the tank with the BGK.
You see, (and you're going to think I'm crazy) I have 8 fish tanks up and going and although the tanks are not species specific, they are parameter specific.
I refuse to expect a fish to "adapt" to less than ideal parameters for that species just because I want it.
<Agreed; some fish are adaptable of course, but others will inevitably do poorly in the wrong conditions. You simply need to know your fish.>
I believe that each tank should meet the specific requirements of the fish I want to put in it. Therefore, the BGK has her own 72 gallon tank that she shares only with her Brochis catfish and one Bristlenose because they share the same parameters and the Brochis and the Bristlenose don't mind the extra current that the BGK needs (plus there are areas where the current isn't as strong).
<Quite so. Brochis are sadly underrated, but a much better choice than Corydoras in larger, deeper tanks. Things like Megalechis and Hoplosternum are good too, being even more hardy and a bit more robust, so good choices with adult oddballs that aren't actually predatory, just big.>
Even though the water parameters would fit the elephant nose, I still would not put that species in this tank for the reasons you mentioned plus the fact that elephant nose don't like a strong current.
<I think they're a bit more adaptable than you might think. Bear in mind that even a brisk aquarium current is barely a dribble compared with the flow in an African river! So provided there are resting spots below or behind rocks where they can rest, these sorts of fish should tolerate water flows up to 8-10 volume of the tank per hour. But yes, for sure they won't appreciate turbulent flow in open tanks without shelter.>
The tank I want to put the elephant nose is a separate 75 gallon that has only the two rope fish, the spiny eel, and a Bristlenose.
<Oh, he'd be fine here.>
It has a sand substrate, plenty of plants (the plants have a tendency to "move" as the spiny eel likes to tunnel through the sand), and plenty of caves to hide in. It has a Cascade 1000 canister filter which provides a pretty good current, so I keep the spray bar submerged to slow it down as the rope fish don't like a strong current either. That is the tank I was going to put the elephant nose in. The rope fish are 6 and 8 inches and the elephant nose is just under 4 inches, so I don't think I have to worry about them trying to eat the elephant nose (they haven't bothered the spiny eel and its about 4 inches as well). Plus, I feed only frozen foods (bloodworms, baby brine shrimp, daphnia, Cyclops, and chopped up grocery store fish or prawns) so hopefully that satisfies their craving for meat.
<All sounds good. Elephantnoses go wild for plankton, so your baby brine shrimps, daphnia and Cyclops should fit the bill nicely! Once settled they're pretty tough, even bossy, but these tankmates sound about right for them.
Good luck, Neale.>
Re: Tough Decision to Make      6/15/17

Many, many thanks! The couple that have this fish live on (or near, I haven't been to their home) Mountain Home Air Force Base in south central Idaho. It's about a 2 hour drive for me, but they were so excited (and I think relieved) when I just called them and told them you gave the "thumbs up" that they offered to meet me halfway in Boise.
Their movers are coming this Friday to get the rest of their belongings, and they fly out on Saturday, so we've arranged to meet tomorrow when I can pick up the fish. I'm really excited, (ok, and a little bit nervous as I won't be able to return this fish if something goes wrong), and your comments have given me the confidence to go ahead.
<At the very least, you're giving this fish its best chance of a secure future. Keep us posted.>
Thank you for all you do!
<Most welcome. Neale.>
Re: Tough Decision to Make      6/16/17

Well, here he/she is! I hope I reduced the picture small enough for you to download. (lol) I'm sorry about the picture, but he/she wasn't in the mood to "mug" for the camera and this is the best I could negotiate.
<Not an easy species to photo, trust me!>
It's understandable though, he/she just spent the last 3 or 4 hours in a plastic butter tub driving in a car and then suddenly finds himself/herself in a whole new world.
<Quite so; this is an intelligent animal (for a fish, anyway) sensitive to its world. Give it time.>
Is this species always so thin?
<Nope. While the "stem" between the tail and body is thin, the actual girth of the body should be relatively chunky; Mormyrids are valued food fish in the wild. At the least, you want the belly area to be distinctly convex, and regular small feedings (even 3-4 per day) is a good way to help this fish put on weight. They have big appetites (perhaps something to do with their electricity production) and do need good quality food, and plenty of it. Daphnia, brine shrimp and the like are useful; if you can get them, clean wormy foods are excellent, perhaps Microworms but ideally small earthworms and the like. Tubifex and bloodworms definitely taken, but not without their risks.>
Is there a way to tell if its male or female?
<Probably, if you're another Mormyrid. Females are probably a bit more chunky when mature (commonly the case with fish) but they actually identify gender by using their electric sense, so far as we're concerned, they basically look the same. If you know any physics specialists with an oscilloscope, it's actually possible to hear their clicking with the right tools. Very neat. Cheers, Neale.>

Re: Elephant Nose - Peacock Eel question. Comp.        11/24/17
Ok, this morning I had to move the Eel. When I woke up, it was at the top of the tank hiding behind the spray-bar from the filter and the Elephant Nose was pacing back and forth as if "stalking" it.
<Oh! Doesn't sound good.>
So now the Eel is in the BGK tank with its two Ropefish buddies (72 gallon). I don't think the Eel will mind the extra current as there are a lot of places to hide or get out of the current, and plenty of sand to dig through - is that correct?
<Yes; Spiny Eels enjoy strong water currents, provided they can burrow into something that keeps them secure, like soft sand or a hollow tube. They are riverine fish, so more than able to move about in strong currents. They
just don't like constantly swimming. What suits a Black Ghost should suit a Spiny Eel just fine. Very similar requirements, and indeed, to some degree ecological niche -- nocturnal predators on small worms and the like.>
I'm really glad that this territorial behavior indicates that the Elephant Nose is doing well as I truly love this fish, but now he seems to be going after the Ropefish.
<Uh-oh. Any chance of adding something to disrupt this behaviour? Some active midwater dither fish (Congo Tetras would be African species that fit the bill nicely) might help to give the Elephantnose something to target
without being vulnerable themselves. Synodontis species are good too, having what Loiselle referred to as a 'Mosaic' approach to retribution -- not actually aggressive if left alone, but like the prophet Moses, more than able to wreak bloody vengeance when pushed, so tend to be left alone by all but the most psychotic tankmates. A group of adult Synodontis nigriventris should be a good choice, and usually aren't nippy or bothersome, something which can characterise the larger Synodontis. There are some gentle giant Synos out there though, if you want a single, bigger catfish; Synodontis eupterus springs to mind.>
The smaller of the two Ropefish is now in the same spot the Eel was this morning while the larger is swimming circles up and down the wall beneath him.
<Does sound like territoriality, in which case adding -- not removing -- fish can be the solution, by spreading out aggression. Another tip is to remove the aggressor, rearrange the tank, and after an hour or two, return the aggressive fish. With luck, this resets the dynamic as the aggressor has lost his territory, and now behaves more like a newcomer. Sometimes, even giving the aggressor a 'time out' by confining to a net or something inside the tank can work, by reminding him he's not top dog, and there's someone even more terrifying in the jungle, namely, the fish net!>
Now the Internet is full of advice, some good - some not so good - about the Elephant Nose (and everything else of course.) and every article I've read says the Elephant Nose is a schooling fish and shouldn't be kept alone. Is that true?
<Right, here's where things get complex. In the wild, yes; these fish occur in big schools. HOWEVER, in fish tanks it's very difficult to keep a big enough group that they coexist. As you know, they're electric fish, and
constantly jostling for position by jamming each other's frequencies. It's something we can't see or hear, but presumably stressful. So if you keep, say, three or four specimens, you usually end up with just the one dominant
fish. Think about Piranhas and you've got much the same problem. I guess if you had space for six specimens it'd be worth a shot, but you'd need a really big tank, given adults are 20 cm/8 inches or so in length. Bottom line, outside of jumbo tanks, it's simply easier to keep a singleton. They can't do much harm to L-number catfish or Synodontis, so those are reliable tankmates, and equally, a school of Giant Danios or Congo Tetras isn't going to be overly bothered by them simply because they're too quick for it to harass.>
Because my Elephant Nose seems to be telling me it wants the tank to itself, and that's ok.
<Certainly, for whatever reason it doesn't appreciate the fish it sees as competing for food or hiding places.>
I have another 75 gallon tank up and running that houses only a 3 inch Baby Whale and a 2 inch Senegal Bichir (an odd couple, I know, but the Bichir is the only fish the Baby Whale has terrorized to madness) and it would be
quite easy to move the Ropefish to that tank.
<Sounds a teeny-tiny Bichir! I'd treat that chap very delicately at this point, as they are a bit sensitive when this small.>
I just want everyone to be healthy and unstressed (me too if that's possible!).
<Hopefully the above will help. Cheers, Neale.>
Re: Elephant Nose - Peacock Eel question       11/24/17

Well, I can't do anything about trying to get new fish today because of the holiday, but I do have 5 Serpae Tetra in my community tank who seem to LOVE to chase each other around all the time anyway and are too fast for the
Elephant nose to catch - would that work, at least temporarily?
<I would not... Serpae Tetras are highly social, and highly hierarchical, little nippers -- really scaled down Piranhas! Fin-nipping is part of the way they feed, so they're poor choices for pretty much anything. Nice fish
to look out, and fun, but best kept in large groups on their own in shady, planted tanks. Cheers, Neale.>
Re: Elephant Nose - Peacock Eel question       11/24/17

And yes, that Bichir is very small. I got that one and another that is barely an inch long from a guy who wanted to try to use them as feeder fish for his 5 Jack Dempseys.
<I... uh,... don't know what to say... so pointless and cruel. It's not like JDs are obligate piscivores in the wild, and the farmed fish will eat most anything.>
Apparently he found new victims elsewhere and wanted the bichirs gone.
<I despair of my fellow fishkeepers sometimes. Neale.>
Re: Elephant Nose - Peacock Eel question       11/24/17

I completely agree. Want to hear the "kicker?" He has his own business - aquarium maintenance.
<Yikes! In all honesty, he may be a great fishkeeper for all I know. But he really needs to break the feeder fish habit! Expensive, risky, cruel, and without any kind of benefits for any of the fish widely kept by aquarists.
I admit there are one or two very rare things, like South American Leaffish, that really do need a supply of home-bred livebearers or Killies to stay alive, but most everything else can and should be weaned onto alternatives. Cheers, Neale.>
Re: Elephant Nose - Peacock Eel question       11/24/17

Hey Neale, if you don't already think I'm crazy, this may make up your mind. I moved my Ropefish out of the elephant nose tank because the EN was harassing them to the point that they were throwing themselves against the lid trying to get out. But even that didn't stop the EN's tirade - he started in on the plants and seemed to almost be thrashing around the tank.
I did water testing and results came back no ammonia, no nitrate, and nitrate was definitely less than 20 ppm (this tank's water change day is Tuesday). I put my Neon Tetras (8) and Harlequin Rasboras (7) in with him and he became a mad bomber blasting his way through the schools repeatedly.
I had a random thought that this fish is experiencing some sort of short-circuit and tried to remember when this behavior actually started. I thought it started shortly after I put in a terracotta "cave" I made for them. He acted weird when I first put it in, but he always acts weird when I make any change to his tank. But looking back, this was different.
Instead of hiding, the EN was approaching the terracotta cave in an almost aggressive manner, and then backing away from it - repeatedly. Also, the Peacock Eel was lying under the sand right next to the terracotta cave when
the EN first attacked him. So I looked up terracotta and it was described as a "clay type earthenware, glazed or unglazed, most commonly used in the old days as an ELECTRICAL INSULATOR..." (ok, lights are going on now!) The article went on to say that all clays are the best electrical insulators because they completely resist the flow of electric charge? So I took the terracotta cave out (half an hour ago), and although the EN is still pretty
active, he's just swimming around, he's no longer charging the rasboras or the tetras. This is really important because he still has two decorations in the tank, his other caves, that are ceramic but these items are glazed
(the terracotta cave I made is not). Do you think it's possible this could be setting off his aggressive behavior through some distortion of the electrical signals this fish relies on to function in its world?
<It's possible, but I'd have thought less likely than the 'buzz' from the wiring in and around the tank, such as the lights. But still, empirical evidence always trumps the theory, so if removing the cave helped, and he's now settled down, then I'd definitely call this a win if I was you!
Elephantnoses use their electricity in two main ways, for navigation and for communication. So far as navigation goes, it's why they keep their bodies so stiff and straight, and as they release electrical charge, they detect any distortions in the field they produce, and that tells them where objects are. It's kind of like radar I suppose. The communication thing, as we've discussed, includes a lot of hierarchical elements because there is a best frequency for the navigation field, and only the dominant one will use this frequency, forcing others to use less ideal frequencies. The lower down the pecking order you are, the worse the frequency you're left with.
(If this isn't a good metaphor for Net Neutrality I don't know what is, but I digress...) Things that interfere or reflect with the frequency the dominant fish is using will be seen as a social threat. That might be another dominant fish, in which case they fight, but I suppose it could be some unusual object that somehow reflects or distorts that frequency, irritating the dominant fish. Being just an animal, albeit a relatively smart one, he or she would be angry, but likely to transfer that aggression to another fish rather than some dumb rock, because he or she knows rocks aren't social threats! Anyway, that's my theory for now! Good luck sorting it all out, Neale.>
Re: Elephant Nose - Peacock Eel question    11/25/17

I think your theory is correct - thank you for your help!
<Maybe a hypothesis is a better word! But anyways, good luck, Neale.>
Re: Elephant Nose - Peacock Eel question    11/25/17

If I could trouble you with just one more question, and then I promise to drop it, but I'm sitting here looking at the Elephant Nose, I can see he is a lot calmer, but still agitated to a lesser degree. He seems to be fixated on one corner of the tank. It's where the terracotta cave was but its no longer in the tank at all. But what is over there are the tiny, baby bichirs. Could the EN be recognizing their species by sight and see them as a physical threat, not a social threat.
<By sight, no; Elephantnoses have poor eyesight, and recognising a 'species' isn't really something fish do. A big giant Bichir would be seen as a threat, sure; a baby one just registers as background detail. As always with animals, beware applying human motives and human senses to their world -- we/they are simply too different, and making comparisons is the pathway to confusion. Elephantnoses primarily react to electrical stimuli, possibly other fish, but mostly fish that are emitting electrical fields themselves. They will also react to things that conduct electric fields in a novel way, such as balls of aluminium foil in their aquarium.
They are gregarious (so do get lonesome, I'm sure) but also hierarchical (so become aggressive in small groups). Their secondary sense is taste, which is what their 'trunk' is all about. So foraging is important to them.
Think about ways to make their lives more interesting perhaps, by offering live foods -- baby brine shrimp for example are very popular with some -- which takes them a while to find and eat.>
The bichirs went into that tank at the same time as the terracotta cave (I made it for them as a safe haven).
<I would simply observe for now. It may well take time for all to settle in, and settle down. Cheers, Neale.>

Spiny Eel Compatibility       3/21/17
Good Evening WWM Crew! I have read the WWM page regarding Spiny Eel compatibility, and while the page was very informative, I did not find the answer to my question. I have a 75 gallon tank with three Rope Fish in
it. The tank has been up and cycled for 4 years now and is filtered by 2 Cascade 1000 canister filters (I'm all for over-filtering), and is set up for the Rope Fish. I use pool filter sand for substrate, RO/DI water with Equilibrium to replace minerals, Alkaline Buffer to boost kH, Acid Buffer to maintain a pH of 6.6 - 6.8, and Stability to keep my biological filter fully charged. I also have a tank cover that is both grated and smooth to prevent escapes. Haven't lost a rope fish yet.
<Good; they are escape artists>
The tank is fairly heavily planted (java fern, wisteria, and Rotala) with two large ceramic caves on opposite ends of the tank. But I recently read an article on Peacock Eels (Macrognathus siamensis) and was completely charmed by such a beautiful fish. So what I was trying to find on the WWM page regarding this fish is whether it would make a good tankmate for three Rope Fish.
<This Mastacembelid would be fine here>
Also, if it would work, would a Peacock Eel be happy as the only one of its species with the three Rope Fish or does it need others of its own kind.
<Is fine either solo or in a group>
I ask because although I have plans to move them up to a bigger tank, its at least 6 months away, and with the potential size of these species, I want to be careful not to overstock - even with the big filters. Your opinion would be greatly appreciated. Thank you!
<Welcome! Bob Fenner>
*Life is not about how fast you run or how high you climb, but how well you bounce. ~Vivian Komori*
*Renee *
Re: Spiny Eel Compatibility        3/22/17

Thanks again!
<Welcome. BobF>

Spiny Peacock eel fungus... Mis-stocking iatrogenic prob.s, no reading       5/3/15
<... what re the punctuation here? Are you a non-native speaker?>
first of all I'm resuming it the best I can, I'm using your saltwater question because sincerely, the website is confusing and the freshwater help, didn't help a little bit, I have just got 29 may, a peacock eel, it was in my 66gal tank, with 8 discus,
<Not compatible.... Mastacembelids like very different water quality than Symphysodon>
18 tetra neons, 7 ember tetra, 4 checkerboard cichlid, 1 Polypterus senegalus and 2 p. delhezi,
<.... What? You have Bichirs in here too? You need another few tanks to sort these disparate species out... READ on WWM re each species requirements and compatibilities. What you have here will NOT work>

and 4 gold sport dwarf Pleco (please don't bother me about number of fish in tank,
<You already know?>
as the discus will pair up they are going to 30g breeding tanks, the smaller fish(all but the Polypterus) are going to be relocated, the final fauna plan is to be 3 P. senegalus, 2 P. delhezi and the discus that don't pair(and hopefully the peacock eel)) It was beaten bad, I don't know by whom, but it was, i didn't saw it since she was hiding most of the time in the
driftwood, until today morning she was normal, I was worried about her feeding habits, was giving Tetra ColorBits, frozen shrimp and a national fish food(name is Poytara, but they have no English website),
<Ahh; I see you are a NNS>
I didn't saw it eating so I just put some frozen shrimp at night and hoped it would eat when the others were not active, this morning it appeared almost upside down, I immediately separated it in a 15gal hospital with a (don't remember the English name, but the black pieces you put under gravel, though without gravel, just ceramic rings) and driftwood, put some national medicines (being one based in Acriflavine for fungus and one based in green malachite, Methylene blue, magnesium sulfate, potassium chlorate and copper sulfate that one for bacteria), am on my way to get some Melafix
<Worthless. READ before writing us... PLEASE!>

or anything they may offer at the best LFS around here,
and am wanting help as to what to do to try to save it's hale
<.... Let's have you start reading here: http://wetwebmedia.com/FWSubWebIndex/spinyeelsmonk.htm
and the linked files above. READ Gustavo... w/o your delving into matters here, your spiny eel and likely other fishes will perish. You need to separate them ASAP by their water quality needs and temperaments. Bob Fenner>
Re: Spiny Peacock eel fungus

Me again, just read that copper is no-good-idea for them, there should be about 0,015 grams of copper sulfate(30 drops = 1,5ml, there is 1g for 100ml in the medicine) in these 15gal, equal to 0,00025g of copper per liter, I am going to make a 5 gallon water change without the copper based medicine anyway, just wanted you to know
<You ARE reading! Good. BobF>
Fwd: Spiny Peacock eel fungus     6/4/15

Would you please elaborate WHY they should not be together ?
<... this TOO is archived on WWM. No need for me to re-key over and over>
"*Water requirements:* Soft, acid water preferred" taken from your link, discus also like soft and acid water (on that we agree right?)
<And quite warm...>

Where Polypterus are different, they can take a huge range of water parameters, I'd like to know why would it be a bad mix ?
<Simply that the group of fishes you listed don't have much overlap in preferences, tolerances...>
Also, it currently has the anti-fungus and MelaFix that I got earlier, it is still breathing but in bad shape, could the crew please first and foremost address the emergency and later talk about water param.s ?
BTW does NNS stand for Non Native Speaker or something else ?
<This is it; yes>
That's all, yes, I might have done some useless or dumb thing, it was my emergency protocol, do you have some better one to teach me ? Sorry by any typo I made, writing in the cell while in a moving vehicle(I am not the driver, relax)
<Read or go elsewhere.
Bob Fenner>

Peacock eel sick?    2/22/14
We have a peacock eel in a 60 gallon planted tank with gravel. We did try to make him a hiding area in the gravel with a pvc pipe, but he showed no interest.
<A faux rock or log works better>
 We have had him for several months and he has always been very energetic with activity and feeding. Yesterday, he started just laying at the bottom of the tank lethargically and seems to have stopped eating. We tried hand feeding him but he sort of shook his head and backed away (we have been able to hand feed him before). We have never done any live worms but often feed him the frozen blood worms.
<Unfortunately; these sewer fly larvae have such issues... Better to at least mix in some other foods>
 He also seems to be "breathing" heavy. We really love our atypical peacock and were hoping you'd have some advice as to whether or not he is sick
<Is sick... nutritionally>
 and if we can do anything to help him. We tested the water and everything was in the safe zones. Water temp stays between 76-78 degrees. We have community fish plus tiger barbs, a clown loach (to eat baby snails that we didn't know reproduced so well), and other bottom feeders.
-James Shelton-
<Do look into live or frozen/defrosted blackworms... Spiny eels (Mastacembelids) find them very hard to resist. Oh, and please peruse the archived files on this family of fishes on WWM. Bob Fenner>
Re: Peacock eel sick?    2/22/14

Thanks for the quick response.  We are making changes today.
<Ah good. BobF> 

Peacock eels wasting away?    9/19/12
Hi, very informative site you have here. I believe I have an issue with my peacock eels. I originally had two and just lost one. The tank is 65 gallons in a community setup.
<Mmm, hard to keep an eye on such spiny eels in large settings, get them fed amongst competing tankmates>
The smaller peacock was about 4 inches, I had him or her for about 6 months and then it refused to eat. Being that I have a few very spastic weather loaches in the tank I was worried that they were scaring him away from the cut red wigglers
<Might well need smaller food/s. See WWM re >
 I've been feeding them, so I moved him back into a 20 that I keep as a hospital tank until his demise. My other peacock eel is still in the 65, and is starting to worry me. He seems more active but a lot of his activity is spent running up and down the tank walls, he still eats and the loaches don't seem to bother him, I usually feed an appropriate sized worm every other day or so. Recently the six inch eel has began to appear skinny though, and I'm worried that something is wrong and I'm going down the same track. Water conditions are 6.8 ph, 0 ammonia, and around 10 on nitrates.
<These are okay>
I do about a 15% water change bi weekly
<I'd change at least this amount, more likely 25% every week>
and replenish any evaporated water every few days. Filtration is an Aquaclear 110 modified to give the tank some current.
<Keep the top covered to prevent these fishes leaving>
 It's got about 8 separate pieces of driftwood and many live plants. Are internal parasites common in spiny eels?
<Mmm, yes. Folks in the import part of the trade are encouraged to batch treat (via foods) w/ an anti-protozoal (usually Metronidazole) and anthelminthic (typically Praziquantel)>
 That's kind of what I'm leaning towards but could definitely be wrong. I just don't see how he can be eating and getting thinner. I haven't saw <seen> any of his waste. In this tank I also have my prized possession, a 5 inch fire eel that seems very plump and healthy(his much larger tank of the future is a work in progress but coming soon). I don't want to see him get sick. Everything else in the tank seems very healthy. What should I do?
<I might move the six inch Peacock to a smaller system... easier to observe, determine what is going on. Bob Fenner>

Sick Peacock Eel? White on tail and head?    5/24/12
Firstly, I just wanted to say thank you for volunteering to help fellow aquarists with their problems, it is greatly appreciated.
<Thanks for the kind words.>
Here's some background: I have a 75 gallon with a built in corner overflow/and underneath wet dry filter, 80F, with 1 piece of driftwood, 2 smooth large rocks, 2-4" of pool filter sand substrate, and live Anubias, wisteria, java fern, recently added Vallisneria, and just added yesterday, Salvinia minima. Current stock is 1 ~5-6" peacock eel, 2 ~4" Senegal bichirs, and 1 ~4" African Brown Knife, 1 mystery snail, and various other snails. Water change regime is 30% every 3-4 days, and they are all being fed frozen bloodworms, frozen Mysis shrimp, and frozen brine shrimp daily currently, I am looking for live blackworms and probably will try to get some small earthworms as well, since I know bloodworms aren't the best foods.
<All sounds good.>
I got my ~5-6" peacock eel probably 3 weeks ago or so (I got him from PetSmart, in a tank that had gravel, which now I know was bad right from the get go),
<Can be bad, yes. Once their skin is damaged, bacterial infections are very common.>
and right from the beginning he has had odd behavior. (I intended to QT him, but my QT tank sprung a leak, so into the main tank he went) The first day was normal, he spent the whole day buried with just the tip of his rostrum out, night time he would come out. Second day, he spent with his head out, night time he would be out. Third day he spent 75% swimming about happily in the open, and since then he doesn't burrow himself anymore at ALL, he is out and about 100% of the time, swimming around happily. I see him more frequently then I do my bichirs. He eats the bloodworms quite voraciously, and will nibble on the Mysis shrimp sometimes.
<All sounds good and normal.>
When I first got him, on the 3rd day I noticed that he had a small kinda clearish whitish bump underneath his chin, but I wasn't sure if it was an illness, or if it was just how their heads look (I've never had spiny eels before). I've kept an eye it, and it hasn't grew at all, however, yesterday I noticed a very small white bump on his "spine" by his tail (it's not Ich). And looking closely this morning, it looks like he has a little bit of a white/clearish layer on the side of his snout. His behavior is very normal though (well normal for him), actively swimming in the tank during the day.
<I see.>
From what I've read, I am assuming its the start of a  bacterial or fungal infection?
<Could easily be. I would treat aggressively, ideally in a quarantine tank, but if you must, in the display tank. I'd use salt/heat together as per Whitespot, and also treat with a reliable antibiotic for bacterial infections such as Finrot (Maracyn 1 and 2 for example work together very well). Other types of medications might be used, but copper and formalin MUST be avoided as Spiny Eels react to them in a very unpredictable (and often fatal) way.>
If so, what would be the best treatment given his current tankmates and the fact I have live plants? I was planning on using 2 teaspoons of aquarium or non iodized table salt per gallon of water, and that was it so far. I've used Melafix/Pimafix combo when my bronze Cory a few years ago had a severe cotton fungal infection that ate both her side fins and tail and was on half her body, and she pulled through and her fins even grew back to my surprise, so I have high praises for it, though recently have read many bad reviews on how it "killed their fish." so I am unsure. I can't afford to buy a new QT tank at the moment, so whatever treatment has to be used to treat the display tank.
<Bob F. isn't a big fan of Melafix, and frankly, given what it is, I wouldn't use it to medicate any fish once it was sick. But yes, some people have had good results with it. Corydoras are tough animals right out of the box, so it's not impossible for them to get better even with mild medications like Melafix. If your Spiny Eel is feeding and happy, you might try the Melafix alongside the salt/heat, and give that a go for the next 2-3 days. But if the white area on the head shows any sign of expanding, I'd switch to the antibiotics. And honestly, I'd skip the Melafix myself and go straight to the antibiotics. Do also be aware of Lymphocystis, a fairly common problem among Spiny Eels. Not fatal, but unsightly, and apparently connected with environmental issues even though it's immediate cause is a virus.>
Thank you very much in advance!

Re: Fiddler crabs versus peacock eel 10/21/08
Thank you so much for the fast response!
<Most welcome.>
Well I do have a sand/gravel substrate, however the aquarium store had large gravel.
<Hmm... in my opinion, plain smooth silica sand is the way to go, particularly with small (sub-20 cm) specimens.>
And the eel was buried in there when I got it. Do you think it is possible that the eel got the infection at the store?
<Quite possible.>
I watched the eel quite intently and he never buried himself.
<Possibly prefers the hiding places available above the substrate. In any case, they feed by pushing the rostrum (the "trunk" on the nose) into the sand to uproot insect larvae and worms. So even at that level, sand helps.>
He actually spent most of his time swimming near the top of the water.
<They do indeed like swimming among the roots of floating plants. They're great escape artists though, so be warned that they're also apt to jump out, if they can.>
Also do you have any suggestions on what I could do to get my tank better prepared for a peacock eel?
<Do read my article; that's everything I know about them!>
I have three small Cory cats, will they be a problem for the eel?
<Does rather depend on the size of the tank and how much food you put in. Assuming you were generous with the food, these fish might get along just fine. The real problems come with "bullies" like loaches and Plecs that will keep the Spiny Eel away from its dinner. Earthworms are the secret to success with the Mastacembelidae, and they will thrive on these tasty morsels.>
I guess I should let you know that I have a 55 gallon tank with a mostly sand substrate. There is some small white gravel mixed in with the sand.
I have got Platies, swords, mollies, tiger barbs, 2 rainbow fish, paradise fish, the Cory cats, and the crabs. Everybody lives perfectly fine together. I usually put a small amount of aquarium salt in the water. Would this be recommended for an eel?
<I suspect the Fiddlers are on borrowed time. They're amphibious and will spend all their time trying to get out. The vast majority of specimens in freshwater aquaria last but a few months. It's a shame they're sold at all, to be honest. Adding "small amounts of salt" won't really have much effect either way. They won't make any of these animals healthier, but if you want to waste your money on boxes of salt, then go ahead, you aren't doing any harm either.>
<Cheers, Neale.>

General habitat questions re Mastacembelids, Gouramis   7/26/06
 Hi from New Zealand. Im planning to purchase 3 striped peacock spiny eels and have been searching the internet for 3 days solid trying to gather information. <Is about, but not easy to find... the Net will be much better... soon> Most sites contradict another one so Im all confused. I plan to have 9 Gouramis in the tank as well and two fake rocks that have lots of hiding places, some fake plants, low watt lights, Eclipse Aquarium Hood, and some walnut gravel as it has very small smooth pebbles. How many gallons will the tank need to hold? <Mmm, the "bigger the better"... at least 200 liters...> What dimensions do you suggest? <More "flat" than tall and narrow... to provide surface area for gaseous exchange, habitat for these types of fishes> Am I on the right track with my plans? I just want to get it right so the critters dont suffer. Thank you in advance. Emily <Please read here: http://wetwebmedia.com/FWSubWebIndex/matacembelids.htm and here: http://wetwebmedia.com/FWSubWebIndex/anabantoids.htm and the linked files above. Bob Fenner>

Some Questions about Spiny Eels - 05/22/06 Hi, <<Hello>> First off your site is very helpful and I have learned much from it. <<Is good to hear>> However I do have a problem that I couldn't find an answer to on Google or your site. <<Okay, let's see if I can help>> Im new to aquariums and about 5 weeks ago I purchased a Striped Peacock Eel. <<Read here and at the links in blue:  http://www.wetwebmedia.com/FWSubWebIndex/matacembelids.htm >> At first he didn't eat much (actually hardly at all) but a couple of weeks back he decided to eat as much as he could get.  I would like to know how many 8-10 mm long pieces of earthworms an eel about 7-8 inches should safely consume each day. <<Hmm...would think at least 3-4 pieces would be fine.  Live Blood and Tubifex worms would be relished as well, and will add some variety to the diet>> Also he is outgrowing his home/cave rather rapidly <<Indeed, can reach a foot in length>> so should I try to find him a new hideout (the gravel is a bit to harsh for burrowing) or attempt to possibly put new finer gravel in his half of the tank (during a partial perhaps?). <<I kept some of these eels a few decades back (did I really just say that?!), quite interesting creatures as I recall.  A fine/soft substrate is best/ideal...along with some plants/hiding places...and subdued lighting>> I want your personal opinion/s as well a reasonable answer/s so that is another cause to actually Email you guys and gals. <<No worries mate...I hope I've been helpful>> Thanks in advance, Matt <<Regards, EricR>>
Some Questions about Spiny Eels II - 05/23/06
Wow thank you very much. <<Quite welcome>> I was feeding him as much as 8 pieces and before I decided enough was enough and he still wanted more lol. <<Yes, can be quite glutinous.  Best to feed smaller portions several times a day>> However I know they like to hide and that they like "soft" substrate, I wanted to know if it would be a good idea to change part or even all of the substrate during a partial water change or add a larger hiding spot. <<Would depend much on your filtration setup...but I think changing out parts of the substrate with partial water changes over the course of a week or so would be safest>> Thanks again, Matt <<Always welcome, EricR>>

Peacock Eel questions... sys., comp.   4/26/06 Hello! I just found your site, and it's great! Anyway, I have a few questions. I currently have a peacock eel and 4 mollies (2 Sailfins, 2 Shortfins) in my aquarium. I have read in some places that Peacock Eels like brackish water, <Mmm, can tolerate some...> and so do mollies, but other places say that the Peacock Eel is completely freshwater. <Many Mastacembelids are brackish... not this one. Please see: http://filaman.ifm-geomar.de/Summary/SpeciesSummary.php?id=50400> Do Peacock Eels benefit from marine salt in their water? <Not much, no> How much salt should I add is this is the case? <A minimum amount...> Also, I have seen a 'Figure 8 Puffer' in my local fish shop, and was also wondering if this species is a suitable tankmate. <... no. Too likely to bite the mollies, spiny eel> I have also heard that they are brackish. <... please see WWM re> Any other information about suitable tankmates for my mollies and my Peacock Eel would be greatly appreciated! Paul <Paul... time to read my friend. Learn to/use the indices, search tool on WWM. Bob Fenner>

Striped peacock eel info   3/16/06 Dear Robert, I am new to eel care and have some questions regarding eel behavior.  My eel is approximately 6-8 in long (I'm not sure exactly because he doesn't stay still) and appears to be healthy.  I have only had him a few days and he still looks pretty nervous about his new home. <Typical> I have a 55 gallon aquarium with 1TB aquarium salt for every 5 gal.  I am unsure about this but have read they do ok in brackish aquariums. <To an extent, yes> My main question is that could my 6-8 in eel eat a 3.5 in Senegal bichir or 5 in violet goby? <No, could not>   My bichir is terrified of my eel and the violet goby is MIA at the moment.   <The latter may have "jumped out"... look about on the floor... or be hiding.> Also I am unsure he is getting enough to eat I have tried fresh raw fish, cut Nightcrawlers, and shrimp pellets.   I have heard and read that these are all foods accepted by eels but I am nervous anyway.   <Best to offer some live worms, insect larvae that sink...> would a sort of community feeding spot work? <Mmm, could> None of my other fish are terribly voracious and I was thinking of a watering hole type situation.   If you could help to unravel some of this I would appreciate it. Sincerely, Matt Tompkins <I do hope your livestock all settle-in... they should be compatible... that is, "get along" with another. I would not add any more salt than you mention... and would try black worms, Tubificids for your Mastacembelid eel for now. Bob Fenner>

FW Eel  1/16/06 Hi, there! First off, I will begin by thanking whomever is reading/answering this e-mail. I am a relative newcomer to keeping FW eels. I currently own two such specimens. One 7" striped peacock eel, and one 4" zig-zag, or tiretrack eel. I purchased the tiretrack eel from Arizona Aquatic Gardens (azgardens.com) whose incompetent 'staff' told me that the zig-zag eel would grow no more than 10" or so. I have found since that my eel may grow to 3', which poses a dire problem to me. < Fire eels, Mastacembelus erythrotaenia, gets big, like three feet long. I have seen them in public aquariums at least that big. But the tire track eels that I am familiar with, Mastacembelus circumcinctus, stay around eight inches or so.> <<There are other "tiretrack eel" species. RMF>> However, there is an even bigger dilemma I am confronting today: is there such a fish as a dwarf starry night eel (*Caeco**Mastacembelus spp.), *and what size does such a specimen attain? Is it a strictly FW fish? What, pray tell, is the recommended pH and aquarium size of such a specimen? I have tried to Google this one out, and have even gone through the German and French websites, with very little success. I am contemplating the purchase, but I am cautious, as the seller (AAG) states such a specimen will not grow past 6". Is this even possible, in your opinion? Thanks again for answering my question and I bid you good day. George < While diving in Lake Tanganyika a few years ago we saw many eels. Some were only 4 inches long and swam like little seahorses while others were at least a foot long. Look at Caecomastacembelus, Afromastacembelus and Aethiomastacembelum on fishbase.org. These are the three genera of eels from Africa. All that I know of get up to a least a foot and a couple get up to two feet. The Lake Tanganyikan ones require hard alkaline water with the others probably tolerating almost any kind of water. The eel you are looking for may be in these groups.-Chuck>

Capitalization, Spiny "Eels" - 12/06/2005 Hi, my name is Silas. I <Your name, I, beginnings of sentences.... PLEASE capitalize....> have two peacock eels I got from a local PetSmart. Tonight I went to clean my tank and I noticed some little worm like things swimming around. I thought they were parasites but then I thought they could be baby spiny eels. <Highly unlikely that these are baby eels. Also, they are not necessarily parasites. Please search on WWM.... start here: http://www.wetwebmedia.com/FWSubWebIndex/fwinvertfaqs.htm .> I was wondering if they can have babies and how big they are. <I recommend a Google search on "breeding spiny eels" or "breeding peacock eels" for more information on the topic than we have available here.> I don't know what to do, so I e-mailed you. Please try to e-mail back soon. the "things" are really small and look like parasites so please tell me if they can be babies or if they are parasites. <Read, my friend; much to be learned here and elsewhere.... I suspect your worms are "visitors" of a sort, indicating an overabundance of "food"/nutrients in your tank. Wishing you well, -Sabrina>

Peacock Eel average questions/conflicting answers I just discovered your website and I LOVE IT! I've been a constant freshwater fish fan for years and I have just purchased a peacock eel (Mastacembelus erythrotaenia <<This is a/the Fire... perhaps Macrognathus siamensis? RMF>) and I was just wondering if there was any way to tell the difference between the sexes. Also I have done as much research as I can and I have found so many conflicting reports it makes me dizzy. I just want to make sure I have the basics right so that he/she can live long and happy. For now he's in a 29 gallon (and in about 4 to 5 months to be moved to a 75 gallon) and the temperature goes from 70 (at night) to 75 (in the day). He is in something the pet store called "red sand" but it isn't red and looks like normal sand. The pH sometimes varies from 7.1 to 7.4. He seems to love the sand and only 5 minutes after releasing him he had found a perfect spot to dig and stick his head out. Some of the websites I visited said that they could eat flakes or pellets, is this true? for now he seems happy just to eat bloodworms that come out of this feeder when they are unfrozen. I was thinking (because I know in general spiny eels like live food) to add 1 male guppy and 2 female guppies so that when they mated he could eat the fry. My brother has a soft shelled turtle that he does this with and it seems to work rather well. In a couple of websites they said it would be ok to put him with a knife fish. My knife fish is very friendly and for the short time I had a sting ray in there (babysitting for a friend who's bacteria had all died after his younger brother poured in a bunch of VERY old fish medicine) the knife fish actually made friends with him and would swim just above him and tickle him with his lower fin. These are a lot of questions but I really want him/her to be happy. (I also like to know whether they are male or female so I can name them). >> Your eel should be called "fire eel" by its common name. The peacock spiny eel is another species, that does not have the red lines on its body. If it is a fire eel, it will get to a very large size, that means over three feet long, and he will need a tank large enough to live as he gets older. They do like live food, especially live earth worms. He should be fine with a knife fish. You may want to make sure that your temperature is more stable, best between 74 and 80 degrees Fahrenheit. Good Luck, Oliver

Feeding peacock eels I just purchased a small peacock eel and was wondering if I was feeding correctly. He/she is about 4-5 inches long and I'm feeding shrimp pellets. I read in the information on spiny eels that they won't bite and chew their food. I don't think my eel's mouth is large enough yet to eat the shrimp pellet whole but I dropped a pellet near him (he's burrowed and sticking his head and part of his body out) earlier and it's gone now. Will they eat the pellets once they've softened? Or do I need to resort to frozen food (I live in a college dorm that allows only fish tanks and I don't have access to a store that sells live food so my method of feeding is rather limited)? <Please read here: http://wetwebmedia.com/FWSubWebIndex/matacembelids.htm > In addition to that, I was wondering what would be the best remedies for the most common infections, like Ick. I'm using a product currently with my other fish called CopperSafe by Mardel (Active ingredient: Chelated Copper Sulfate) in combination with a product called MelaFix (it says it's safe to use with scale-less fish). CopperSafe seems to work really well with my other fish, including a Pictus cat, who came in with Ick. But you mentioned that metallic medications don't work well on eels. What should I look for in an anti-Ick medication when it comes to peacock eels? Should I just dose the tank with non-iodized salt? Sarah <Please read over WWM using the Google search tool there, with these questions, product names... I would not use Melafix for anything, nor copper compounds on Mastacembelids or Pimelodid cats... Read my friend, before purchasing livestock, using toxic chemicals on them. Bob Fenner>

Questions about Peacock Eel Hi folks!  <Howdy Carol> First of all thank you for a very informative website! I am a constant reader, and have learned much by reading your articles and responses to other people's questions. <Welcome> I have my own questions for you now, regarding a Peacock eel. I raise Mystery Snails and my nursery tanks are nearly overflowing.  <These are great animals... when/where raised "properly"... unfortunately, most all the ones that go "through" normal wholesale channels are either DOA or very close to it...> I would like to relocate some snails to my 55 gal tank which houses a 5" peacock eel. Would this be safe? <Should be... small snails might be eaten, but this Mastacembelid does not eat larger snails by and large... however, worms of all kinds are history> I don't want to create a scenario that is going to result in snail carnage. I have some Sterbai Corys (10) in the tank with the eel. The LFS was adamant about Peacock eels being 'very, very gentle' and no problems at all with snails. However, I don't know if I can trust them as we all know that LFS's are renowned for misinformation. <All must by evaluated by you in the final synthesis> I have read on the Web conflicting information about Peacock eels, some say that they are extremely aggressive and will take small fish (like Corys) when they get large enough to do so. <I have never seen this... and have handled hundreds of Peacocks... other spiny eels that get much larger (e.g. erythrotaenia, the Fire) don't even touch armored cats...> I have also read that Peacocks are very gentle and won't eat anything aside from live worms, perhaps the odd bit of fresh shrimp, and/or ghost shrimp. <This is my opinion> Can you please tell me the truth... would such an eel take mystery snails, or bite off their tentacles? My snails range from babies of a few mm long to full sized adults. I have even contemplated another tank just to house the eel, but I've run out of room for more tanks quite some time ago. (I guess I could rearrange the furniture again though...).  Also, how do Peacock eels do when housed with members of their own species? <Very well... are extremely social animals> I was advised to get a second eel to make mine feel more 'at home'.  Thank you so much for any information you can give me! Sincerely, Carol <Thank you for writing. Bob Fenner> 

Purchasing some spiny eels I was thinking about purchasing some spiny eels from an online store. Is it wise to have a striped peacock, a Zig Zag, and a fire eel all in the same tank? <Not problematical in terms of them getting along, feeding/foods, having different habitats if this is what you mean> Also, the site I was planning on ordering from said that spiny eels eventually needed 29 gallon tanks... but I read about people having to put them in 100 gallon tanks, what's the minimum size I can have for one and does it affect what size of tank I need if I have one of each of the aforementioned spiny eels? <Mmm, at least a hundred for the Fire Eel... gets quite large over time, in good health... the others could live in 29 gallon systems (well-covered!). Please read here: http://www.wetwebmedia.com/FWSubWebIndex/matacembelids.htm and the Related FAQs (linked, in blue, at top)>   I read that the eels will eat crustaceans, so I assume a blue crayfish would be a bad tank mate...  Is it wise to order online?  Or would you suggest going to a local breeder or distributor?  Thanks in advance. <Both sources could work... or be trouble. The spiny eels are quite tough if cared for well, and doomed if not... Seeing them ahead of purchase is definitely a bonus, better start if you can find, order them locally. Bob Fenner>

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