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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 and leave.  Full Size Link

Updated 1/17/18, Ask us a question: Crew@WetWebMedia.com
Brackish INDEX to Articles and FAQs;
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Daily Q&A replies/input from the WWM crew: 
Neale Monks, Marco Lichtenberger, Eric Russell, Chuck Rambo, Bob Fenner, are posted here. Moved about, re-organized into individual FAQs files!

Re: Brackish moray ID      1/4/17
Hello Marco,
<Hi Ben.>
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: http://www.tansuigyo.net/a/gao/x/551.html
<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 Fishbase).
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 link
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 starts.>
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
<Cheers, Marco.>
Re: Brackish moray ID     1/11/18

Hello Marco,
<Hi Ben.>
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 or videos.>
Thank you and Best Regards,
<Have a nice day.>
Ben Haryo
<Cheers, Marco.>
Re: Brackish moray ID      1/12/18

Hello Marco,
<Hi Ben.>
Nice to hear that your winter is warm, I hope this is good for your tropical fishes!
<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 flashlight.
<This would be good. Maybe we can get a proper ID instead of just guessing wildly.>
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 to Fishbase).
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 observed.
<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!
<You, too!>
Best Regards, Ben
<Cheers, Marco.>

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 here.
<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 submerged traps.
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 noodles.
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.
<Thanks Ben.>
Warm Regards, Ben
<Cheers, Marco.>

a bunch of morays in a bucket      12/28/17
Hello Neale, hello Marco, hello all,
<Hi Ben.>
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: http://www.wetwebmedia.com/fwsubwebindex/fwmorayart.htm 
Young G. tile look like this:
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 of you!
<Hi Ben.>
(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 inconvenience).
<<Accepted. B>>
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.
<Very good.>
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 aquarium care).>
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 anomaly?
<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 white spots.>
Well, thank you for your time & have a nice weekend!
<No problem. Have a nice weekend, too.>
Best Regards, Ben
<Cheers, Marco.>

Re: Brackish moray ID      12/31/17
Hello Marco, I hope your weekend will be a splendid one!
<Hi Ben.>
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 declined.
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)     1/1/18
Good Day Marco,
<Hello Ben.>
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
<Cheers, Marco>

Re: Brackish moray ID      1/3/17
Good day Marco,
<Hi Ben.>
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 blotch.>
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.
<Sounds good.>
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
<Cheers, Marco.>

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