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Cardisoma sp. (likely C. armatum).
Southeast Asia, Indonesia Land Crabs. Soap-Box Crabs for how
they're individually shipped (in plastic soap-dishes closed
with rubber bands) to prevent cannibalism. To eight inches
across... Not a community tank item... Actually not totally
aquatic... if you're lucky, yours will crawl out of the tank
Updated 1/17/18, Ask us a question: Crew@WetWebMedia.com
Brackish INDEX to Articles and FAQs;
Other Specialized Daily FAQs Blogs:
Planted Tanks, Ponds,
Daily Q&A replies/input from the WWM crew:
Monks, Marco Lichtenberger, Eric Russell, Chuck Rambo, Bob
Fenner, are posted here. Moved about, re-organized into individual
Re: Brackish moray ID 1/4/17
Allow me to continue our discussion,
I am thinking about other possible moray species that matches my eel,
which are not Echidnas nor Gymnothorax.
In Fishforums.net a poster listed some species of morays that enters
brackish & freshwater (I think this was quoted from WetWebMedia ;) One
of the species mentioned, Uropterygius micropterus, is interesting,
because when I see this picture here:
<Not sure this is Uropterygius micropterus, but it's possible. Too bad
the dorsal fin is not visible on the picture. Uropterygius micropterus
has a light brown background color with a net of darker lines (see
Gymnothorax richardsonii has a more greenish color with a dendritic
pattern. All Uropterygius spp. have a low dorsal fin limited to the area
of the tail, while Gymnothorax spp. and Echidna spp. have a higher
dorsal fin that starts behind and above the gill opening. The genera can
easily be told apart with the eel in front of you by this character.>
Some of Mr. Eko's eels which he keep in his other brackish tank has the
same patterns on the body with the Uropterygius Micropterus in the
Chinese link above, though the coloration are different, that eel in the
above are more dark brown, while Mr. Eko's eels are more grey-ish brown
(except the one he gave me, it is green-ish brown).
<Compare to G. richardsonii, especially have a look where the dorsal fin
All of his small (<30 cm) eels he said were caught in brackish river,
while the larger marine ones were from coral reefs around small islands.
Price differences also reflect this, the colorful fully-marine morays
costs a lot
more than the small brackish ones.
BTW, the small eel just ate a piece of thawed frozen shrimp. Interesting
how fast it adapts with my aquarium, just a few days and it already ate
frozen meal (smeared with garlic, thank you for your advice!), while my
smallest E. rhodochilus still refuse anything else than live meal, even
after living here for months!
Well, that concludes my observation today. Thank you for your kind
attention & have a nice day!
<Have a nice day, too.>
Best Regards, Ben
Re: Brackish moray ID 1/11/18
Warm greetings from Indonesia. How's Germany today?
<Warmest winter I remember.>
I observed the eel and see no visible dorsal fin that starts above the
gill opening. So there is a possibility that this is an Uropterygius eel
instead of a G. richardsonii or E. rhodochilus?
<If you don't see said dorsal fin on the eel in question, but you are
able to see it on your Echidnas, the mystery moray likely belongs to the
genus Uropterygius (Anarchias would be another option).>
<Sorry Ben, I can't make out any detail in the vid, it's too dark and
blurry. You should use some additional light source when taking pictures
Thank you and Best Regards,
<Have a nice day.>
Re: Brackish moray ID 1/12/18
Nice to hear that your winter is warm, I hope this is good for your
<I don't think they care. It's the same temperature in the house and
their tanks all year round.>
Sorry for the bad quality of the film. I hope to borrow a better camera
later, to take a better picture of my eel, or a cell phone with a strong
<This would be good. Maybe we can get a proper ID instead of just
In any case, if my eel is actually an Uropterygius micropterus as I
assumed, it is already 20cm maybe more, so I guess it's near adult (not
baby eel anymore), as maximum length of this species is 30cm (according
So, if it's really U. micropterus, then we confirm what Fishbase said is
correct (that it is both brackish and marine). It also seems to be happy
in its 1.008 sg aquarium, and are very docile in temperament, it is very
friendly with the E. rhodochilus and G. polyuranodon, no aggression
<Good to hear.>
When I am back to Sumenep, I'll ask Mr. Eko in which part of the river
he captured them: Was it at the river mouth, or further inland, did he
used a submerged trap or did he picked them up in shallow waters. This
way we could have some more info about the habitat of the eel.
<That's a good idea. Most of such useful information is lost with
export, it's great you are close to the source.>
Too bad this species is not so common as pets, as I think this eel could
be one of the easier ones to keep. It is not as pretty as E.
rhodochilus, G. polyuranodon or G. tile, but it is not so hard to feed
and not so shy, mine seems to spend almost as much time swimming outside
the pipes as waiting inside. It also does not run away from my hands
when I am cleaning the aquarium, interesting eh?
<Yes, especially since Uropterygius species in general are reported to
spend most of their lives hidden in rocks and mud, but to be honest: not
much is known about the behavior of members of this genus at all.>
Well, thank you and have a nice day!
Best Regards, Ben
Re: Brackish moray ID 1/17/18
Good evening Marco,
<Good morning Ben.>
Greetings from Indonesia!
I am aware that there are not much information about fresh and brackish
water morays, so indeed, as an eel-enthusiast who lives close to the
source, I'll share whatever information that I can gather from around
<Kudos to you.>
As for our mystery eel, I visited Mr. Eko this afternoon, and asked him
a few questions about the eel. His answers are as follows:
1. The mystery eels that he has, were captured in the river in Java, a
bit farther from the river mouth (estuarium), but he said this species
are also known to inhabit not only on the river, but also the area
around the river mouth and the beach. So, they can be found in both full
saltwater and light brackish. They are from shallow waters, usually
found in sandy beaches hiding in broken corals or under clamshells, or
in the soft mud of the rivers.
2. They are known to hunt crabs and shrimps on the shallow waters of the
beach and rivers. They can burrow their bodies in both soft sand and
mud, but they are more active in swimming around, than other types of
morays which spent much of their time burrowing or hiding. They could
hunt during the day or during the night as they please.
3. These eels were usually not captured by fishing hook, but by
4. They are not territorial, plenty of them can be found together in a
small area, often bunched together under a clamshell or a rock, like
So I thanked Mr. Eko for his info, and he promised to inform me if there
are any other strange eels he captured or obtained. Before I left, he
offered me to buy a pike conger baby at discount, as apparently he has
one left. He told me that the pike conger were captured in the same area
where they captured the mystery eel. But I declined (pike congers are
known to be aggressive and has sharp teeth), and instead I bought
another mystery eel from him.
So now I have two of these "mystery eels", I hope they will be happy in
my aquarium. Mr. Eko took pictures of the conger and the second mystery
eel, I attached it here. His shop is not as dark as my kitchen, so maybe
these pictures are better for ID ing the mystery eel?
<Yes, much better. Can't see details of the head, but at least the body
coloration is visible. It's definitely no G. richardsonii, G. tile, E.
rhodochilus, G. polyuranodon. The coloration of the body matches
Uropterygius micropterus quite well, so this ID is probably right. The
ecology you describe above also concurs with what is known about this
species. Only that it seems to live so openly is something I had not
expected from a Uropterygius species. I think this eel can be added to
the list of moray species in captive care.>
That concludes my e-mail for now, I will share to you more from my
research when I get new information.
Warm Regards, Ben
a bunch of morays in a bucket 12/28/17
Hello Neale, hello Marco, hello all,
Warm greetings from Indonesia to all you amazing people at WetWebMedia.
So, I visited an ornamental fish procurer, the one who actually captured the
fishes. I asked for fresh or brackish water morays. He showed me a bucket full
of eels that he captured several days ago from a river in the
north of Jakarta, not far from the estuarium river mouth.
Here are the pictures of the eels.
So, which one is Gymnothorax Tile? I can recognize one tiny Echidna Nebulosa,
but the rest of them I have no clue. I am not even sure that they are all
morays. The guy who captured them all made no distinctions, all of those eels
are "Belut Muara" to him (Belut Muara = eels being caught in brackish water).
<The pictures show too little detail for a proper ID. Would need to clearly see
the heads of most of the eels. As you already know there is E. nebulosa and
probably G. richardsonii. There might also be one (the grey eel with tiny spots)
or two Gymnothorax pictus, which are easily IDd by the dark spots in their eyes.
However, I cannot see the eyes on the pictures.
Gymnothorax tile are grey to brown with yellow the golden speckles. The older
the eel, the less golden speckles. See here for some pictures:
Young G. tile look like
The pictures you mailed of Mr. Septian's eels also show some G. tile and one
potential G. pictus. >
Thank you & have a wonderful day!
Best Regards, Ben Haryo
<Hope this helps. Marco.>
Brackish moray ID (file size fixed) 12/30/17
Hello Bob, Neale, Marco, and all my WetWebMedia friends, a good Friday for all
(Dear Bob, sorry for the large files, my bad. I have re-sized the file and
re-send the message. I hope this time it's in the correct size. Sorry for the
Marco, thank you for your kind explanation. Brackish water is fascinating, isn't
it? I like the concept of brackish and near-freshwater estuarium as nursery
ground for various juvenile marine moray species, so they could get the
nutrients from freshwater and cover to hide from marine predators. Our estuarine
waters are indeed dark and muddy in many places, unlike the clear bright waters
of the coral reefs just a few kilometers at the open shore.
I have made plans in the future to visit some of those estuaries & rivers in
North Java and in Yogyakarta & record their salinity levels & record the tales
about morays from local fish catchers.
<Nice. If possible compare the salinity at the bottom of the estuary with the
surface. Can be quite different.>
I will keep you informed.
I am also interested in marine aquarium, but maybe later when I have more space.
Space is a problem for me as I cannot find place in my house for another
aquarium. I often found myself donating my pet fishes to other friends, not long
ago I donated my Anguilla bicolor to a friend who has a larger aquarium, as it
has grown almost to 1 meter in length & looking very stressed & cramped in mine.
It had spent almost 3 years in my aquarium.
Currently I am also looking for a new home for my Monopterus albus, it has grown
to 70 centimeter and has shown signs of stress, before it's very active, now it
became lethargic, often perched itself on top of the filter (glad my aquarium is
covered!) or bury its head on the sand (glad the bottom of my aquarium is sandy,
not gravels!). I have
donated other fishes in the past as well.
<You seem to like all eels, not only morays. As far as I know, M. albus does
travel into brackish waters, but prefers freshwater in the long care (and
Well, today I went to my hangout at Sumenep, where fish lovers hang around.
I visit my friend Mr. Eko, a specialist of brackish water fishes. Not only
catching fishes in our estuarium and rivers near the sea, he also quarantine
them and acclimatize them then supply them to ornamental fish seller. He has
cement pools for this purpose, as well as various brackish, fresh and marine
aquariums. He is an aquascaper too. He showed me his lovely Echidna nebulosa,
which is very fat and is an adult (about 50 centimeters). He proudly told me
that he kept this eel for almost 2 years in this brackish water, and describe
how the Echidna survived a jump out of the aquarium for 2 hours! It's the best
eel for aquascaping marine tank, he said, because of durability, docility and
beautiful skin patterns. His tank is about the same size with mine, but mine is
a bit longer. I sampled and tested the water on the E. nebulosa tank with my
hydrometer, it's 1.012-1.014 after 3 tests. He told me that it was originally
the water from the river where the Echidna came from, but he does regular water
changes to acclimatize the eel. His aquarium does not look so appealing, with no
sandy bottom and only a handful of dead corals for the hideout of the Echidna.
But the Echidna does looks healthy. I wonder how that's possible, as to my
knowledge, E. nebulosa cannot survive anything below 1.018, so is this an
<Surviving and thriving are two different things. E. nebulosa are very hardy and
it's not the first time I hear it was caught in brackish waters.
1.014 is already mid brackish to high brackish. It's well possible the eel will
survive this for months or a few years, but nothing I can endorse for permanent
care based on the biology of this species.>
Knowing my love for eels, he showed me a low-water aquarium full of small eels,
he said they're totally brackish. I sampled the water and it's 1.008 - 1.010
after 3 tests, so rather similar to my aquarium. I asked about the Latin name of
the small eels and he said he has no clue (kind of expected).
So he gave me one, and asked me to study the eel and tell him what species it is
according to science, and I can give it back to him later. It's very very small,
maybe only 15 centimeter, and when I put it on my tank, it looks comfortable and
it snuggled itself under my largest Echidna rhodochilus. They looks compatible
in the pipe, they're almost the same in color and I noticed it also has white
blotches on the mouth. Is that a juvenile E. rhodochilus?
<Probably. Can't be sure. The pictures are rather blurry and dark.>
I look at Fishbase and noticed that Echidna leucotaenia also has white blotches
on mouth. What do you think it is, dear Marco?
<Based on what I see: E. rhodochilus. Echidna leucotaenia has more and different
Well, thank you for your time & have a nice weekend!
<No problem. Have a nice weekend, too.>
Best Regards, Ben
Re: Brackish moray ID 12/31/17
Hello Marco, I hope your weekend will be a splendid one!
When I look at the "mystery" eel and how similar it is to E. rhodochilus, I
think there is a big chance that you are right. The morphology are similar with
my larger E. Rhodochilus, and they even breath in the same rhythm.
<You can try to take better pictures (more light, acuity, more detail of the
head) of your mystery eel. Then we can work out a better ID. The last pics were
so dark and blurry, I can only guess its ID by a white spot I suspect. E.
rhodochilus is easily IDd by its uniform green to brown coloration and a larger
white spot at the rear part of the lower jaw which extends to the upper jaw
below the eye.>
What are other possible candidate? Maybe G. richardsonii?
<G. richardsonii can be IDd by a dark green dentritic pattern on a lighter
background color. Looks nothing like E. rhodochilus.>
I just read in a webpage that this species stay small, and also inhabit
estuaries. Will G. richardsonii thrive in 1.008-1.010?
<I doubt it. Though it does occur in shallow waters with brackish salinity it's
most often found in marine lagoons as far as I know.>
Are they as docile as E. rhodochilus throughout their lives?
<I kept G. richardsonii in the past. Mine could not be trusted with small
fishes, but got along well with other small morays.>
As you can tell, I like eels, not just morays. Actually Mr. Eko offered me one
of his newly-caught pike congers, the one with lovely blue-ish dorsal fins. Very
beautiful fish, but I heard it's rather vicious when wild-captured, so I
Back to our E. nebulosa. Mr. Eko told me that small E. nebulosus are frequently
being caught in the estuarium, while the larger ones are more common on coral
reefs and on rocky beaches. Maybe it's like what you said,
the younger ones hides in the estuarium, as they grow older and bolder, they
venture to the sea. If that's the case, then it's a humane practice to keep them
in full marine, as brackish is only a temporary hangout for them.
<I agree with that.>
Well, thank you for your kind patience and guidance. I will keep you informed
about my findings. Best Regards, Ben
<No problem. Looking forward to your findings. Cheers, Marco.>
Re: Brackish moray ID (file size fixed)
Good Day Marco,
I tried to take better pictures. This eel seemed to change colors
depending on its surrounding.
I hope these pics are clear enough for IDs.
<I fear they are not. I cannot see the coloration of the head and the
pattern on the body with enough detail.>
This eel and his friends were caught in a brackish river in north Java,
and has been living in a brackish tank for several months.
<Does your eel have the telltale white spots of E. rhodochilus or the
dendritic pattern of G. richardsonii? You can also compare your eel to
the ca. 65 species found in Indonesia here:
If you try to take pictures again use much more light (will also help with
sharpness) and maybe borrow another camera.
Thank you & Best Regards, Ben
Re: Brackish moray ID 1/3/17
Good day Marco,
Sadly you are right, I cannot get any better quality pictures with my current
cell phone. Also, my kitchen _is_ dark. Good for the morays, not so good for
photography :/ So, I will try to find a better equipment to make pictures. I can
take the eel out , bring it outside and take pictures, but I don't have the
heart, it's such a cute little eel... When I can borrow a better camera or cell
phone, I will make pictures again.
I checked out the Fishbase list and also this article below:
I observed the pictures of Bakasi (G. richardsonii) on the article above, indeed
the color and body-patterns are not similar with my eel. The Bakasis has
brownish and grayish color and beautiful body-patterns. Mine are plain.
Also, the Bakasis are described to be caught on the coastal areas.
<Also known from estuaries when young.>
Mine are caught in a brackish river, several kilometers from the sea. My eel has
the same body type and color with E. rhodochilus (brownish green/greenish brown)
but it has no white blotch on the cheek, just white blotch on the mandible. Most
logical explanation that it's a freak baby E. rhodochilus that has white blotch
on the mandible only.
<Probably E. rhodochilus if it's uniform brown to green with a single white
Or it's another species that happen to live in the same environment & behaves
similarly & has the same color.
Anyway, Mr. Eko said I can keep the eel for as long as I wanted, see if it could
live well and happy in my1.008 sg. If it thrives, he will let me have it. If it
doesn't look happy, he will take it back. So it's a good deal.
I joked to him, If it's a new species, I'll name it Muraena ekonii after him ;)
The Fishbase article is very useful, thank you for sharing! I have seen some of
the morays described there. Interesting that Fishbase mentioned some morays as
living in both marine and brackish (like Gymnothorax pictus)
and even all three environments (marine, brackish and freshwater) like the
Gymnothorax meleagris. Maybe most Gymnothorax species
<and many Echidna spp.>
are capable to enter brackish and freshwater from the sea, but not all has the
adaptability to thrive long-term in non-marine environments.
<That's what I think. Especially the young, the adults not so much.>
Well, thank you for the advice & discussions, I learn something new everyday!
Best Regards, Ben