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FAQs on Mastacembelid, Spiny Eel Identification

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,

Spiny Eel ID 2-9-08
Hi, I was wondering if someone from the WWM Crew might be able to help me figure out the sort of Spiny Eel I have.
<Hello! Merritt here!>
When I got the eel I have (it was more then a year ago) she (or he) was very timid, very small, and wanted to hide all the time, as I would assume that most eels do. I was told at the time that she was a ‘Black Leopard Eel’, as I couldn’t actually find anything on that being even a real name of a fish I tried to find out what she was on me own.
<Smart move>
For the first few months I never saw much of her or what she looked like.
Now that’s she’s gotten used to her surroundings, I’ve been able to get a good look at her markings almost every day now for the last few months, and was finally able to get a good picture, but I can’t find anything that looks like her. I’m starting to wonder if I’m either not looking in the right spot, or if her markings are just to light?
<They will develop as she matures.>
If it helps here’s some info on how she acts and her growth. She went from about 5 inches long and just under and inch tall in the middle when I got her, to just under 14 inches long and about an inch and a half tall in the middle in about a year.
She loves frozen blood worms and likes frozen brine shrimp, and her favorite seems to be ghost shrimp (but I only give the ones I breed so it’s not to often she gets those).
<Nice variety in diet, keep it up!>
She gets along great with the two (about 8 inch) Plecostomus that have. But she did attack one of two angel fish (They were about 6 inches tall at the time when she was still ‘little’) during the night of the first day after they got in the tank after quarantine. I clearly don’t plan on adding anything else to the current tank or when I get a bigger one for them. During the day she will come to the surface and take cubes of food from my fingers and oddly (never had another fish do this) likes her sides rubbed.
<Many species of eels like to be touched.>
She will also try and ‘attack’ the fish in the tank next to hers. I assumed the first time she was hungry but even when she has leftovers that she doesn’t eat she still attacks, similar to a Betta.
Hopefully between the picture, and her temperament someone might be able to tell me what exactly it is I’ve been keeping in there.
And also please don’t think that I was irresponsible for getting something without knowing what it was first. Normally I make sure to know exactly what I’m going to be putting in my tank long before I get it. However when I had gone on my trip that ended up with the eel, I had just finished cycling a new 30 gallon tank set up, and my list was for a Betta, and few swordtails as I was planning on just having a well planted tank. But there was a 5 year old with his dad and one of those 2 gallon Betta bowls not even big enough for a Betta who was looking at picking out the eel. And I had enough common sense about eels that it needed something bigger then that to live in.
<I can understand the saving a fish from death story, I have done it a few times at pet stores. From the picture I think you might indeed have a spiny eel (Macrognathus siamensis) but here is a link to FishBase if you want to be 100% positive. http://www.fishbase.org/Summary/SpeciesSummary.php?id=50400>
The link to the picture is http://i107.photobucket.com/albums/m304/yuugana/dessy.jpg if the attachment didn’t work.
Thanks much Jacob
<You're welcome! Merritt A.>

Re: Spiny Eel ID, Neale's further input to Merritt and querior 2/10/08
Hi Merritt,
From the photo of the spiny eel in Sunday's FAQs, my best guess would be that is not in fact Macrognathus siamensis but actually one of the species in the Mastacembelus armatus/favus complex. The size of the thing is one clue; if the plants are Amazon Swords, then that spiny eel has to be a good 30 cm long, way too big to be Macrognathus siamensis. The colour markings are quite close to Mastacembelus armatus, just restricted to small spots instead of squiggles. In any case, it's a large Mastacembelus spp of some sort, will get to about 70-90 cm in total length, and is predatory. I've made the mistake of keeping these fish with things as big as swordtails, and they get eaten! Cheers, Neale

Spiny Eel questions... ID, sys., comp. 2/26/07
Hiya, WWM. This is Ashley again; the paranoid person with the two spiny eels named Hope and Doom. <Hi Ashley, spiny eel keeper Marco here.> I'm pretty sure they're what I've seen called yellow-tailed spiny eels. (Mastacembelus armatus) <I just had a look at your older mails with pictures and hesitate to agree, because the second picture seems to show that they have a separate tail fin in contrast to an unbroken fin. If that’s right, they are not M. armatus, but a smaller species, probably Macrognathus pancalus (max. 7 inches). Have a look at the tail fin to verify.> They're still going strong, eating like pigs, and uprooting my plants. I have been considering "downsizing" in the fish department, since I have 5 tanks to keep up with now, along with tons of fish, and many other pets. <That’s just the beginning, you are already addicted…> I was wondering if the two eels would be okay in a 10 gallon together (alone). I read somewhere that they stop growing at about 6 inches <Not if they are healthy M. armatus.>. I was thinking about either keeping them in a 10 gallon, or keeping just them, the gold dojo loaches, and the pleco(s) in the 30 gallon. Which would be better? <If they are M. armatus, both tanks are too small in the long run, since these fishes will get 90 cm (35 inches) long. If they are a M. pancalus or another Asian species with separate tail fin, the 30 gallons would ok.> I'm also wondering if the activity of the other fish (various guppies, mollies, platies, the loaches, and the pleco) affects the eels' activity level. They are fairly active during the day, and I'm wondering if I take the other fish out, will the eels' activity level go down? <To me it seems their activity is high, when the tank mates are peaceful, and low, when they are intimidating the eels.> Or do I just have some really weird eels? Thanks in advance for your reply, Ashley. <You are welcome.> Oh, and since they're fairly little, and don't even bother messing with anything bigger than a bloodworm, do you think they would harm 2 two and a half-inch Kuhli Loaches? I was told that they would attack them like worms... <They are probably safe with M. pancalus, but would be eaten by M. armatus>.

Re: Spiny Eel questions... 3/1/07
Thank you so much! I have never noticed that there was any difference in the tails of the different species...They look most definitely like Macrognathus pancalus to me, now that I've looked it up. They do have separate tail fins, not one whole one. Thanks again for your help!
Ashley. <I am glad we could help. Good luck with your eels. Cheers, Marco.>

Spiny Eel IDing...and a few other questions.   1/27/07
Thanks again for your quick reply. I looked at the fishbase pictures and descriptions, and didn't find anything that looked like them, but on one of your Spiny Eel pages, I found a letter from another reader who had what they called a "Yellow-tail Spiny Eel" and it looks exactly like what mine looked like in the store I rescued them from. (Wal-Mart... They were sold to me as Fire Eels.
<M. erythrotaenia they are not>
I knew that wasn't what they were, but they had no idea what the difference was between Fire Eels and other Spiny eels... They were $9 each! It was worth it, though.) I'm not sure if it's the lighting, or if they just changed their colors, but they're both more greyish now. Doom's fins are still yellow, but you only notice it when she burrows in the gravel and when she's up against something. They have these square/rectangle spots all over their bodies, if that helps at all. And right now they're 4 or 5 inches long, give or take a bit, since they never sit still unless they're eating.
  And on the subject of eating, how much frozen bloodworm should I give them?
<Mmm, not too many...>
The LFS was out of the kind that's cubed, so I bought the other kind, the frozen slab-looking thing. I break off about an inch long piece, and thaw it, and they greedily gobble it down. I try to satisfy the other fish with frozen Brine Shrimp so that the eels will have a fair chance at the bloodworms, and it seems to work. I just don't want to overfeed them, but I also have had trouble with previous eels and underfeeding. How often should I feed them? I feed them about 2 or 3 times a week, with a good amount.
  Thanks again!
  Ashley
<Really a matter of subjective evaluation... a look/see at how full... they appear... look up the term "index of fitness" on WWM. Bob Fenner>

Mastacembelus ID and Wild-Eyed Angel - 01/23/2007
Hi, it's Ashley again.
<Hi Ashley, Sabrina with you today.>
You may remember me as the person with the overstocked tank suffering from some sort of poisoning (new sponge, possible chlorine)...Well, they're (the fish) all just fine now, no more deaths, and they're all in the other tank. They seem to be back to normal except for Jack, the Angelfish. He is fine physically, but he hides at the back of the tank when I come anywhere near the tank, (before the incident, he'd beg for food at the front, or just show off his fins) and he also has a 'wild' look in his eyes. And at first I thought he wasn't eating, but he does eat a little. Just not when I'm around. He almost seems as though he's had some sort of brain trauma...is that even possible???
<Mm, possible, but more likely the animal is still recovering from whatever issues they dealt with....  Without seeing the previous correspondence, though, I don't know what troubles they had.>
And I have some pictures of my two Spiny Eels, and I was wondering if you could help me ID them. I believe they are some sort of ZigZags...I am attaching the pictures. The one in the gravel is Doom, as well as the one under a plant, and the paler one is Hope. They have the same markings, but Hope seems paler, and Doom's fins are more yellow.
<The images aren't clear enough for a definitive ID, but I'd wager that they're Mastacembelus armatus, tire-track or zig-zag eels.  You might also consult fishbase's listings of Mastacembelidae: http://www.fishbase.com/identification/specieslist.cfm?famcode=432&areacode= >
Thanks for all you guys do!
<And thank you for your kind words!
Ashley
And I scanned the pictures of the eels, no viruses. :)
<All the best to you,  -Sabrina>

ZigZag Eel question, ID and more 1/20/07
I've been looking for an excuse to E-Mail you all,
<Heeeee! No need>
First question, I'm curious, are you all biologists with extensive schooling or are you just extremely dedicated hobbyists?
<Mmm, a mix... we are all volunteers (I am the common progenitor)... a bit of our backgrounds is posted... http://wetwebmedia.com/WWMAdminSubWebIndex/wwmcrew.htm
Some of us have an academic background in related "life sciences"...>
Anyways, I'll move onto the real question. I need help identifying this Spiny Eel I bought at a local fish store. It was listed as a "ZigZag Eel" and I had just assumed it was a Tiretrack Eel, but I'm not completely sure.
<Mmm, there are quite a few Mastacembelid eels sold as such...>
I've seen a few images of comparable fish but they're all listed as "ZigZag Eels" with little solid information. I mainly need to know if this is one of the big ones or will it max out at (hopefully) 6'' or so? I'm sorry if I'm being an idiot, I'm just having trouble finding a clear line between a "ZigZag Eel" and many of the Spiny Eels commonly found in fish stores.
<You/we're in good company... the best simple course of action is for you to go to Fishbase.org here... insert the above family name (Do you see the tray to drop down?)... look at the nominal species images for an ID... read re the species posted there>
How is their disposition? Will I have trouble with it hurting any of my fish? How about dietary requirements?
<Most Mastacembelids, even the ones that get quite large, are easy going... only trying to eat even small, slow fishes if trained to do so, and/or very hungry... they eat worms of many kinds, insect larvae... can be trained to take meaty foods...>
Ok, about the last question. I know they prefer live food, I've read this everywhere. The thing is, I bought this one maybe two or three weeks ago and he seems fat and healthy. I feed the Needlefish that he shares an aquarium with 'Rosy Reds', which I'm sure, are far too big for him to eat. I also throw in Ghost Shrimp occasionally; however, I'm sure they're also too large for a fish this size. Its mouth seems tiny.
I feed my fish various foods, trying to find the right combination. Here is the (not so complete) list.
Frozen, cooked shrimp (Treat for the Dragon Goby), Algae Wafers (Stopping these right away, they're discoloring my water), Freeze Dried Tubifex worms, Freeze Dried Krill, two brands of flakes and Shrimp Pellets, along with the live foods, the Ghost Shrimp and the Rosy Reds.. Is it possible he is eating and thriving on one of these foods? Which is most likely so I make sure to feed him often enough?
<Small worms and insect larvae (often labeled as "worms" of various sorts) are best for small specimens, species...>
Like I said, it's been 3 weeks since I bought him so I don't think he's starving; he has to be eating something.
Now I need to know about the temperament of this fish. So far everything has been alright, of course he only comes out when the lights are off (it's getting better about this); however, I noticed something alarming the other night. My Dragon Goby shot to the other side of the tank; he's usually calm and never moves quickly for anything. A fish this big is noticeable when he does something like that so I turned on a nightlight to see what was going on. The Dragon Goby was sitting in its 'hole' like it always does but the ZigZag Eel was inside... of him... The ZigZag Eel had about half of its body inside the Goby, the other half through the left gill. I turned the lights on to scare off the ZigZag Eel and it worked. The Goby is fine, he immediately came to the top of the aquarium looking for a treat and a day later is just as healthy as he has ever been.
<Yikes!>
Should this be something I should be concerned about? Or do you think it was a freak accident on the part of the ZigZag Eel?
<I would be concerned... that the Goby try to consume the eel...>
Maybe even an aggressive move? This is the kind of information that the internet rarely provides except for with the more popular species.
I appreciate any help you can offer, thanks.
-WJ
<Perhaps you will pen an article re your experiences here... In discerning the spiny eel species, determining their habitat, foods/feeding, and temperament. Bob Fenner>

Re: Forgot to attach picture. (ZigZag Eel question) 1/20/07
Unbelievable, I knew I would do that.
<Heeee!>
Here is the picture of the Eel I'm trying to have identified. I apologize for the bad picture quality, I had to do this in the dark.
Thank you,
-WJ
<Mmm, does look like a Mastacembelus armatus from what I can make out: http://fishbase.org/Summary/speciesSummary.php?ID=10140&genusname=Mastacembelus&speciesname=armatus
BobF>

Spiny-eel
Hi,
regarding one of the photos on WetWebFotos.com, specifically the one depicting "Macrognathus siamensis", appears to be of Macrognathus aral, sometimes referred to as the striped spiny-eel.
I don't know if you're aware of this, but I thought I would bring it to your attention, I hope you don't mind.
Apart from this, I find it to be a very good site, and should improve as more species are added.
All the best, Dave Curran
<Thank you for this. Will send off to Zo for amending. Bob Fenner>

Yellow spiny tail eel
I have had difficulty finding info on the yellow spiny tail eel. I bought one from PetSmart a few months back, and they were unable to give me any info on it aside from the name.
This particular store has been known to label their fish wrong, so it could be the wrong name.
<Am sure this is a member of the spiny eel family Mastacembelidae, but fishbase.org does not list the common name, even w/o the "tail" in it...>
All I know about it is that it's from the same family as the peacock eel and fire eel, right now is 3 inches, cost me $2 (a lot cheaper than my peacock eel), and that it likes live worms instead of commercial fish food.
<Most mastacembelids do>
If you could supply me with any info at all, such as how big I can expect it to get (it is currently living with my girls guppies and mollies), I would be extremely thankful. My email is XXXX.
Thanx,
Josh
<Josh, what little we have on this group is posted here: http://www.wetwebmedia.com/FWSubWebIndex/matacembelids.htm
and the Related FAQs (linked, in blue, at top). Bob Fenner>

Why does my fire eel have yellow markings?
>Hi,
>>Hello, Marina tonight.
>I have had a fire eel (now about 9") for almost a year.  He was about 4" when we got him. He used to live in a 25 Gallon Eclipse (eel proof) until I bought the new 90 gallon tank back in March. Quick cute story- thought I lost him last winter. Went missing for about 2 months.  Turns out he was living in the hidden compartment eating bloodworms as they got sucked up the tube. No worse for were, but bigger. Didn't suspect a problem until the water level on the filter was way too high.
Anyway, he lives with a couple of zigzags, a black ghost, a golden Gourami, 4 pearl Gouramis, 5 red Serpae, and a tiger barb. Normal for the tank is flake, frozen beef heart and frozen bloodworms.
The big question. Whenever I see a photo of a fire eel it has red markings. Mine is dull yellow.  Any ideas?  Thanks in advance either way.  Great site!
>>I've seen them both ways, and have always assumed that it's just a variance on coloring.  Try this link for some ideas http://www.wetwebmedia.com/FWSubWebIndex/matacembelids.htm
>>I hope this helps.  Marina

Eel ID
hi my name is Maryanne
we have just brought a eel and no one knows what type of eel it is, it has brown coat and dark brown spots and a long head can you tell me what sort of eel it is please. thank you
< Hi Maryanne I would need to see a picture of it to say for certain. It is best to learn about the animals you are going to bring home before you bring them home. Does it look like either of the eels at the link below?
http://wetwebmedia.com/FWSubWebIndex/matacembelids.htm
You could also try using Google.com to search for freshwater eels, or marine if that is what you have. -Gage>

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

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>

Hello!  I have an eel-related question. Mastacembelid ID, Sys. 7/9/06
Hello!  I've been frequenting your site for the last little while once I started getting fish and realizing that what the pet stores told me was for the most part completely wrong.  Your site has helped me tremendously with my Fire Eel (who I've had now for almost 3 months and he's doing extremely well :-) )
<Ah, good>
but I've noticed there is a general lack of information on the "yellow-tail spiny eel".
<Mmm... is sold under a few other common names... Most often as the Zig Zag eel on the U.S. west coast... Old scientific name is Mastacembelus panculus, now Macrognathus panculus: http://fishbase.sinica.edu.tw/Summary/speciesSummary.php?ID=10147&genusname=Macrognathus&speciesname=pancalus>
I bought one of those about a month ago (he is also doing well, so whatever breed of eel he is, the care is much the same of that of a Fire eel.)
<Yes>
and he's grown a lot.
<Good... though won't get as large... 9 inches is about maximum>
  I got him when he was about 2 inches long.  I've looked at various pictures and he seems to resemble a zig-zag eel?
<Ah, yes>
Albeit slightly yellower, perhaps.  Anyway, I've included a picture so perhaps someone can tell me what it is, or if I'm completely wrong in my thinking that he is a type of zig-zag.  Thank you for your help, and I look forward to hearing from you!
-Becki-
<Does appear to be this species to me as well... Can make very interesting, long-lived pets... given initially healthy specimens, good care, consistent maintenance and feeding... As with all spiny eels, do pay particular attention to keeping the top entirely enclosed to prevent them exiting. Bob Fenner>

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