Spiny eel confusion      3/27/15 I recently acquired a spiny eel identified as a Zigzag eel. Which I thought topped out at like 8". Well now I have found their are two eels that are sold as Zigzag eels. One that gets 38" and the other that stays under 12". My question is.. How do I determine which species I have? I have multiple tanks and can home either on appropriately just don't know how to tell them apart. There's no way for me to get a picture of this guy without stressing him to the max. The best description I can give is he's light brown across his back with a darker brown across his middle and is currently about 5" long and thick bodied. <A photo would help here. There are several species sold as Zigzag Eels. The two big species are Mastacembelus armatus and Mastacembelus favus, more often called (in the UK at least) Tyre-Track Eels. These get to around 70 cm (27 inches) or so, are intolerant of one another, and are accomplished predators. Then there are various small Macrognathus species including Macrognathus pancalus and Macrognathus circumcinctus. These tend to max out at around 20-30 cm (8-12 inches) and get along well with each other. Being small, they're relatively safe with other fish, though bite-sized prey like male Guppies or Neons are possibly at risk. Macrognathus siamensis is the Peacock Spiny Eel, and probably the commonest species in the UK trade. There are some African species, commonly called Afromastacembelus, including some stripy species, but they're expensive and you'd probably know if you had one. I would have you peruse this article: http://www.wetwebmedia.com/ca/volume_4/v4i3/Spiny_Eels/Spiny%20Eels.htm Covers most of the basics. Don't forget soft sandy substrate and ideally the addition of a bit of salt to the water. Both these extras make these fish massively easier to keep. Once sick, Spiny Eels are notoriously unlikely to recover, so prevention is practically the only "treatment" in your medicine cabinet. Cheers, Neale.> re: Spiny eel confusion Thanks, Neale. As soon as I received your email the little guy popped out so here is the very best picture I could get. <It is one of the small Macrognathus, likely Macrognathus circumcinctus or something similar. Maximum length is around 20 cm; peaceful; does well in groups; needs a soft sand substrate -- never gravel, that'll kill it eventually -- and feeds on small worms and other live/frozen invertebrates. Medium hard water in preference to soft, with a tiny bit of salt (1-2 gram/litre) used for optimal conditions. Not a brackish fish, but like all spiny eels, a taste of salt seems to inhibit bacterial and parasitic infections that cause serious problems for this family of fish. So ideally keep on its own (certainly not with other bottom feeders) or choose midwater tankmates that won't mind a tiny bit of salt: livebearers, rainbows, hardy barbs, etc. Cheers, Neale.>

Zig zag eels, stkg., more   8/1/12
Hello,   
<Hello,>
I have just started getting into aquariums about 5 months ago. I am addicted to it now. I have a 15 gallon tank now with some phantom tetras, Kuhli loaches, and a zig zag eel.
<I see.>
I am going to buy a 37 gallon tank soon.
<Good. The Spiny Eel in particular will benefit from the extra space. They aren't easy to keep in the long term. Do read here:
http://www.wetwebmedia.com/fwsubwebindex/spinyeelsmonk.htm
Your species, Mastacembelus armatus, is one of the biggest species and should reach around 60 cm/2 ft in length, if not a little more. Obviously even a 37-gallon tank is a short-term fix, and within a year you should have graduated to something 75 gallons or larger. Do bear in mind Spiny Eels are sensitive; you can't wait to buy the right tank when the fish grows -- you need to buy the right tank before it grows otherwise it'll die. I'm not being overly dramatic here. These fish really are sensitive, and once they get sick, they're almost impossible to treat. The 37-gallon tank should be okay for something like the next 6 months assuming your Spiny Eel is small, and doesn't get bigger than 20 cm/8 inches in that time.>
I will put the eel I've had for about 2 months in this new tank. I am going to buy a black ghost knife which I've read is compatible with the spiny eels.
<Can be, but Black Ghost Knifefish are *even* more sensitive fish.>
I was wondering if I could put a tire track eel with the zig zag eel?
<How big is the aquarium you plan on getting? If we're talking 150 gallons, then sure, you should be able to keep both, provided you understand you need a soft substrate for the Spiny Eel and fast-flowing, very clean water for the Black Ghost. Any aquarium smaller than 150 gallons wouldn't work.>
I really enjoy the eels and would like to add another one but not if they don't get along. I have read mixed reviews and nothing solid to go on.
<See, this is the thing. Lots of people buy Spiny Eels and Black Ghosts, and they keep them (they think "successfully") for a few months or a year.
But then these fish die. They think it died for no reason, but almost always, the fish diet because the aquarium was wrong. Too small,  not enough filtration, and in the case of the Spiny Eel, the wrong substrate (e.g., coarse gravel).>
The local pet store has told me they should be fine as long as i by a tire track eel that is close in size.
<The least of your problems. Mastacembelus armatus is a predatory species, yes, and adults can eat quite large fish --  though as a good fishkeeper you would NEVER use live feeder fish! Likewise, Black Ghosts have the potential to eat small, tetra-sized fish, though they prefer worms and insect larvae. But neither species should view the other as threat.>
If this is a bad ideal i would be willing to try other spiny eels, as long as I keep the zig zag eel. thank you so much
<So long as you have 150+ gallons, it's a fine idea. Neither species is easy to keep though, and I'd recommend you stick with the hobby for a couple years before buying a Black Ghost -- they are extremely delicate fish and easily killed by people who don't understand water quality (including nitrate) and the need for high oxygen levels and under-stocked aquaria, which is why you almost never see adults. Mastacembelus armatus is a little hardier, but easily killed by ignorance, and actually does better in very slightly salty water (around 2 grammes/litre) which would be incompatible with the Black Ghost. But it can be kept in plain freshwater, you just need to understand that the moment the fish gets a bacterial infection, it'll almost certainly die, so you have to make sure it CANNOT scratch itself and is NEVER exposed to non-zero ammonia or nitrite levels.
Make sense? Cheers, Neale.>
Re: zig zag eels  8/1/12
Thank you so much for the response.
<Most welcome.>
I have been doing some research and hope  that you don't think I was just jumping into this. I was told that my zig zag eel would only reach 10 inches.
<Not the ZigZag Spiny Eel (Mastacembelus armatus and Mastacembelus favus).
But there is a second species, Macrognathus panculus, that is less often traded but may be sold under the ZigZag name. It does indeed stay relatively small, around 20 cm/8 inches or so, and if you are REALLY lucky, this is the species you have. But it isn't a common species. Do read here:
http://www.wetwebmedia.com/ca/volume_4/v4i3/Spiny_Eels/Spiny%20Eels.htm
That article gives you a pretty good rundown on what these smaller Spiny Eels need.>
That is what was recommended for my tank at the time.  The pet store had tire track, peacocks, fire and zig zag eels. They said the zig zag was the smallest. That has been another thing that i have read online that seems to have different answers.  They are either the biggest or the smallest.  What are the easiest ways to tell it is a zig zag eel?
<Mastacembelus armatus is sandy brown with dark brown markings; Macrognathus panculus is similar in basic colour, bit has smaller markings (more like speckles) and has a very distinctive row of specks, like a dashed line, running along the midline of the flank from gill cover to caudal peduncle.>
Its markings seem pretty obvious and the tail was another indicator (it is not separated like some) which i have read is an indicator of the size being of a bigger spiny eel.
<Don't know what you mean by this.>
I have a small pebble substrate that was recommended for the Kuhli loaches and was told it was perfect for the spiny eels.
<Absolutely not! If by some chance you do have a Macrognathus species such as Macrognathus panculus, it MUST have a soft, silica sand substrate (such as pool filter sand). I cannot stress this point too strongly. Spiny Eels do better with sand. Gravel scratches them, and sooner or later (it's a "when", not an "if") they get a bacterial infection on their skin that is always fatal.>
As of now, i only feed my eel frozen bloodworms
<Will need much more than this. Try finely chopped seafood (tilapia fillet, cockles, occasionally prawns or mussels) and very small earthworms.
Bloodworms aren't a balanced diet, and there's also some risk of introducing disease through them.>
and had read not to feed them feeders cause of harmful bacteria.
<Good.>
However, I will definitely stay away from the black ghost knife.
<Wise. Do also notice in Marco's piece he mentions the use of salt as well. Trust me that prevention is better than cure with Spiny Eels. Adding a little salt needn't cramp your style -- most livebearers and Rainbowfish will tolerate the minimal amount of salt needed (2 grammes marine aquarium salt mix/litre) but if you go up to SG 1.005 and sent the tank up as a brackish system (that's about 9 grammes/litre) then you could instead keep him with all kinds of fun brackish species like Mollies, Knight Gobies, Glassfish, even Violet Gobies if you have the space.>
Now i feel pressure to get a bigger tank asap.
<Ah yes!>
The tank size is somewhat of a problem. I could only probably go up to a 55 gallon.
<Too small for BGKs. They are massive fish when mature, and extremely sensitive to pollutants in the water.>
If a tank this size isn't big enough for a zig zag, is there a spiny eel that would work better?
<As it happens, Macrognathus species are quite sociable, so getting a couple more would help. On the other hand, Mastacembelus species are very territorial when mature, so best not kept in groups unless you have a huge aquarium.>
I have a friend with a 120 gallon tank which his had for 15 years.  If you feel the zig zag eel is going to be harmed in a 55 gallon tank, I will move it to his tank. thank you again.
<Do check which species you have. Send a photo if you want a second opinion. Cheers, Neale.>
Re: zig zag eels   8/1/12
This is very disappointing news.  It seems i have been mislead on a bit of information.
http://animal-world.com/encyclo/fresh/Eels/HalfBandedSpinyEel.php this site is where found some information before I contacted you. The eel pictured in this link is identical to the eel I have.
<Well that's a species called Macrognathus circumcinctus. It's one of the Asian Macrognathus, and as stated before, these are fairly small, gregarious, basically easy to keep and feed, but they do need a soft, sandy substrate.>
The fin is the same, color is about the same.  I am aware the name given is different then what I have given, but as you have probably seen, tyre track, zigzag, and banded eels are being confused with each other.
<If you rely on common names, then yes, confusion will be frequent. Best to stick with Latin names with Spiny Eels.>
I appreciate your complete honesty and all the information you have given me.
<Welcome.>
The substrate is a shock, cause I asked specifically for one that would harm Kuhli loaches and spiny eels.
<Not an expensive fix, so I'd not worry overmuch. I use smooth silica sand (here in England called "silver sand") from a garden centre, and it costs no more than the gravel.>
When I set my new aquarium up, i will use sand.
<Cool. Just be sure you know what you're shopping for, smooth silica sand.
Not sharp sand (obviously!) or coral sand or any of the fancy sands used in planted tanks. Just plain vanilla smooth silica sand. Feel free to add gravel (up to about 10% of the total substrate) if you want to tone down the colour of the smooth silica sand and give it a more natural look, but plain sand on its own looks great and ages nicely, getting much darker than it looks at first.>
I have looked at feeding my spiny eel earth worms, but was told not to until it reached a bigger size.
<For sure.>
I will probably try to feed them as soon I can.  The brackish water idea has never been referred to me. It is a great idea and I am going to look into it.  Is it safe for Kuhli loaches or should i wait to setup my new tank with brackish water.
<Kuhli Loaches cannot be kept in brackish water. Macrognathus circumcinctus isn't a brackish water species, so I'd not keep that species in brackish conditions anyway. Basically avoid water that's too soft or too hard, and if your tankmates allow, add 1-2 grammes salt/litre of water. Kuhli Loaches won't like that, but if you change the aquarium around, bear this in mind and choose species that will tolerate a little salt. It isn't 100% essential, but it can make a big difference to the ease with which they are cared for.>
Please let me know if the link provided helps clear things up or is just more misleading information.
<It's not a bad article at all, though I'd argue with a few minor things, like using "aggressive" when they mean "predatory", and their water chemistry recommendations are the complete opposite of what's stated as their natural habitat on Fishbase.>
Thanks again Neale.
<Cheers, Neale.>
Re: zig zag eels, comp.    8/1/12
Very last time I bother you. Now that the species is known and I feel more confident.  Could you give me just a bit more advice.  Is a 55 gallon take sufficient for this species of eel
<Yes.>
and is it safe to add other smaller species of spiny eels?
<Provided the size difference isn't huge, then yes, various Macrognathus species (but not Mastacembelus) species can be combined. Allow something like 10-15 gallons per specimen, not so much because they're territorial, but so they have enough space to find food. Spiny Eels are extremely easy to starve.>
Recommendations on other fish to add with this species.
<Anything that isn't so small it'd get eaten is a good start. But also leave out anything that feeds from the bottom. You will have a hard time feeding Spiny Eels at the best of times! No loaches, catfish, etc. Your Kuhli Loaches may be small enough to be eaten by the Spiny Eels when they get big enough. Good tankmates would be medium-sized, non-nippy barbs, tetras, Rainbowfish and livebearers (and the last two groups especially if you wish to add salt).>
I know the Kuhli loaches are not good tank mates for spiny eels and I always have had the intention of moving the spiny eel or Macrognathus circumcinctus to a bigger tank.
thanks
<Cheers, Neale.>