My initial hydrometer readings     12/26/17
Hello Neale,
<Marco here again. Got your email in my inbox.>
This is my initial hydrometer readings. The seawater which I took from the beach of Jakarta, is about 1.020-1.021. My well water is 1.003-1.004, and my aquarium is 1.008 sg. so, this means my aquarium is low-end brackish, am
I right?
<I'd call it mid brackish with about 1/3 SG of average seawater, but you also call it high low-end brackish. >
Best Regards, Ben
<Cheers, Marco.>

Re: My initial hydrometer readings & a new G. Polyuranodon!      12/28/17
Hello Marco, Neale and all you wonderful people at WetWebMedia,
<Hello Ben.>
What species of morays (other than the G. polyuranodon and E. rhodochilus that I already have) that would thrive in my aquarium at 1.008 sg brackish water?
<Gymnothorax tile should work, but in my experience is healthier at higher salinities. Strophidon sathete probably would do well with regard to salinity, but gets too large for usual aquariums. I am not aware of any other morays able to permanently live in mid brackish water.>
Thank you & Best Regards, Ben
<Cheers, Marco.>

Echidna rhodochilus, finally. Feeding       10/28/17
Hello Bob, Neale, Marco and all you good people in WetWebMedia, After years of searching, I finally obtained a small Echidna rhodochilus (35cm), and I'd like to share its pictures with you. It's a lovely eel, but very amusing, just minutes after being released in my aquarium, it already terrorized my shrimps and ate two of them.
The previous owner hand-caught this eel from a river mouth called Muara Tawar in North Bekasi, a neighboring city of Jakarta. He already kept this eel in his aquarium for about a year, in the same water from the river where he caught it, and haven't weaned it off live food yet. This particular Echidna won't eat dead shrimp. Since I have steady access to live shrimps, I don't mind this. But I heard that eels love a variety of different foods, so, If I put Sailfin mollies in the aquarium, will they causes harm to the Echidna if it eats them?
Thank you and have a nice weekend!
Best Regards,
Ben
<Hello Ben. Congratulations on getting hold of this fish! Nope, Poecilia species are harmless, at least in terms of thiaminase. They are, of course, the same risk as any other farmed fish in terms of internal parasites and pathogens. Home-bred specimens should be safer, so if you have the space and inclination, producing your own livebearer or killifish feeders is relatively safe (though Poeciliids seem to be plagued with Camallanus worms that could transfer from mother to offspring, so even here, I'd be careful). Gut-loaded shrimps are a safer and more natural foodstuff for Echidna species that have, on the whole, crushing dentition for invertebrate prey compared to the pointed teeth of the piscivorous morays from other genera. Gut-loading is important though because crustaceans tend to be high in thiaminase, hence shrimp and prawn meat being considered an unsafe staple diet for these (and other) carnivores. I will also remind you that 'freshwater' morays lose their appetite when the salinity is too low, so kicking up the salinity may be helpful. Bob and Marco have written extensively on this/these fish; see here:
http://www.wetwebmedia.com/FWSubWebIndex/fwmorayeels.htm
http://www.wetwebmedia.com/FWSubWebIndex/fwmorayart.htm
Cheers, Neale.>

Re: Echidna rhodochilus, finally      10/28/17
Hello Neal!
<Ben,>
Thank you for the kind words & advice. That was fast!
<Thanks for the kind words.>
Again many thanks. I think I don't have the inclination to breed the mollies myself, so I'll have to stick with fortified shrimps for now.
Anyway, there are still some shrimps left in the eel tank, and seems like they'll all be consumed within a few days, so, after they're all gone, how
many days should I wait until I put on some more live shrimp?
<I would not overfeed; with subadult to adult predatory fish, the aim is to offer food only when they're actively hunting. Personally, I prefer the "little but often" approach with predators, offering them small daily meals
rather than infrequent big meals, simply because it limits the risk of regurgitation or uneaten food being left in the tank. Other people prefer a more 'natural' approach where the fish receives a substantial meal, but maybe 2-3 times a week, but taking care to remove any regurgitated or leftover food before water quality was compromised. But whatever approach you take, a couple notes about Morays. First, they hunt by smell. Adding too many food items at once means the 'smell' gets spread around the tank, and the Moray can have trouble finding it. So get some long forceps or something like a kebob or satay skewer, use this to hold a single food item, and place the item somewhere just upstream of the Moray. Wiggling the food enticingly can help, especially if the food is silvery, like a small piece of fish. If the Moray is settled and hungry, it will start hunting.
The second time is to keep the food bite-sized. Morays can't chew, and despite their ferocious reputation, they actually favour small, easily swallowed food items. Once the food item is taken, repeat a few minutes later. If the Moray shows no interest, it's probably had enough, and you can skip feeding until tomorrow or the next day.>
This particular Echidna Rhodochilus is already 30 cm in length so I assume it is an adult, which shouldn't be overfeed, right?
<Quite so.>
And thank you also for the advice for raising salinity when necessary. I'll try to find a hydrometer so I know exactly what is the salinity rate of my eel tank & adjust accordingly. I have access to seawater (the blessed life of people who lives in coastal cities & not far from estuaries :D ) so it's not inconvenient to mix some seawater to the eel tank.
<Indeed! Sounds nice, especially if you can vary the salinity periodically, up or down, as you see fit. Brackish water fish appreciate this, even though they don't need it. Often you'll see them perk up their behaviour almost as if they're exploring a new tank.>
Best Regards,
Ben
<And to you. Cheers, Neale.>
Re: Echidna rhodochilus, finally      10/28/17
Hello Neale,
Again, many thanks for the feeding info & salinity tips!
<Welcome.>
Speaking of feeding, the remaining shrimps are rather large, and when I turn down the lights, they gather above the Echidna's cave. I wonder what's going on? Are they teasing the eel?
<Nope. More than likely scavenging, and if the Moray withdraws to his cave to eat his food, there could be all sorts of small food fragments thereabouts attracting them.>
As in "hah, we're too big for you, you cant eat us, heh heh!"? Should I evict them later?
<Unless they recognise the Moray as a threat, there's no reason for prey animals to keep away.>
Best Regards,
Ben
<Those are quite big shrimps, for sure! But gut-loading with traditional fish flake, Spirulina and, if you can get it, Sushi Nori algae sheets, will all help to boost their vitamin content and turn them into useful food items. There are marine-grade vitamin supplements, such as Selcon, that can be used -- sparingly -- to good effect as well. With freshwater and marine carnivores, a lot of failure over the long term -- months, years after purchase -- may be explained by lack of vitamins, including Thiamine.
Longer term of course, getting your Moray onto a fresh and frozen diet will be helpful. Cheers, Neale.>

Re: Echidna rhodochilus, finally      10/29/17
Good day Neale!
<Ben,>
Thank you for the tips for fortifying the feeder shrimps. I can give them both fish flakes (available here) and the nori seaweed (I think I saw them on a mall somewhere). The Echidna is so cute, it is worth all the efforts to give it a good home.
<Quite so. A nice fish, and like all Morays, amply rewards good care.>
Speaking of home, I just find this video on YouTube, of a Gymnothorax Tile sharing an aquarium with a Polypterus, both seemed to be at peace with each other, and both still retain their huge appetite for food (though their owner seems to be able to wean the G. Tile away from live food & able to give it frozen shrimp...)
https://www.youtube.com/watch?v=bFXue8NHFRs
Is this some kind of black magic, or is there some kind of chemical stuffs involved?
<No, just luck and time. Gymnothorax tile WILL NOT live its full lifespan in freshwater, and that specimens just a baby.>
G. Tiles are supposed to be brackish water to marine species, while Polypterus are totally freshwater species.
<Yes and yes.>
How could they share the same aquarium like this, without affecting their appetite and behavior?
<The "freshwater" Morays certainly do live some months in freshwater, and youngsters maybe even a year or more. But eventually, without fail, they stop eating. Aquarists who fail to give them brackish water usually end up with a starved, then dead, Moray.>
If this is a brackish water setup, maybe the Polypterus has some tolerance to higher salinity?
<Unlikely. While the Ropefish, Erpetoichthys calabaricus, has some tolerance for slightly brackish conditions, I'm not aware of any true Bichirs in even slightly brackish habitats.>
If yes, maybe I'll introduce a Polypterus or two to keep my Echidna accompanied. What do you think?
<Bad idea. Morays make poor companions. The fact they hunt by smell means they sometimes bite their tankmates! I'd tend to keep yours either singly, or in due course, with some large, robust brackish or marine companions --
big sleeper gobies, brackish water lionfish, toadfish, that sort of thing, maybe even Scats and Monos if you had enough swimming space for them. In low-end marine tanks, pretty much anything will work, including robust
Damsels and Sergeant Majors. Any of these would make more realistic companions.>
Best Regards,
Ben
<Welcome. Neale.>

Re: Echidna rhodochilus, finally     10/30/17 Hello Neale, <Ben,> Thank you for confirming my thoughts. Everything I read about G. Tile online pointed out that this particular fish is more brackish to marine than freshwater. <Quite possibly migratory; Fishbase suggests an anadromous life cycle, living in the sea or estuaries, but spawning in the freshwater parts of rivers. In any event, the experience of those keeping this species suggests brackish will work fine long term, but freshwater doesn't.> So, I understand that combination of Polypterus and G. Tile is "suicidal", if it's too brackish, the Polypterus would eventually suffer, if it's too fresh, the G. Tile will suffer. Not good! <Indeed. Suicidal would suggest either of the fish are choosing to die in the wrong conditions -- not the case here!> As for my Echidna, for now I will let it enjoy the tank by itself and its prey shrimps. This little guy really has personality, I noticed that if the lights are bright, it will behave like a dragon on its lair, sitting nicely on its cave. But when the lights are dimmed, after awhile it will start to "patrol" its surroundings & terrorizing the shrimps. Fascinating isn't it? <Absolutely, and precisely how they behave in the wild. During the daytime Morays are inactive but not asleep, and will indeed lurk with their heads poking out, showing an interest in what's happening in their part of the world. At night they become active, and that's when they hunt.> I will eventually get a friend for the Echidna. Sleeper goby sounds cool, and it's a fierce-looking fish, just like the Echidna, so they will make a great conversation piece. <There are some excellent large Sleepers out there, but do bear in mind such tankmates need to be at least as big as the Moray, otherwise biting is a risk; even if the Moray doesn't actually kill the target, its bites can quickly become infected.> I am thinking to get myself a G. Polyuranodon, but I wonder, will they get along together? <Morays can get along in very large systems with plenty of caves, but they can be unpredictable, so I would tend to keep them singly. Do read here: http://www.wetwebmedia.com/fwsubwebindex/fwmorayart.htm There's a section on tankmates.> Have a wonderful day! Ben <It's almost bedtime here, so will save that for tomorrow! Cheers, Neale.>

Re: Echidna rhodochilus, finally     10/31/17
Hello Neale,
<Ben,>
Thank you for the interesting info about G. Tile behavior. Of all three species that is labeled "Freshwater Moray", perhaps G. Tile is the least deserving of the title. G. Polyuranodon perhaps is the most deserving, but even so, I think G. Polyuranodon and E. Rhodochilus will do better in slightly brackish water, as it's their natural habitat.
<Indeed. But I'm not sure any true eel (Anguilliformes) is 100% freshwater -- even the true freshwater eels, Anguilla spp., return to the sea to breed. My assumption would be that freshwater morays will have a marine
stage to their life cycle, at the very least, and even Gymnothorax polyuranodon is rarely found more than a few km inland, indicating that even though adults do seem to be primarily freshwater to low-end brackish, they do need to be able to get to the sea to breed properly (whether directly or via planktonic larvae I do not know, and don't think anyone else does either). Do see, for example, here:
https://www.ncbi.nlm.nih.gov/pubmed/21722111
Plus the various Fishbase articles on freshwater morays.>
Today I went to the seashore to collect some seawater (about two bottles of 600 milliliters), will mix some of it to my Echidna Rhodochilus aquarium sometime later, to change the salinity, and let's see how the Echidna behaves afterwards.
<Cool.>
I am still unable to find any local fish store which even know what a Hydrometer is, and I am too poor (for now) to buy it online from abroad, but I'll keep searching.
<For brackish, they're not essential. If you mix, say, one bucket of seawater with three buckets of freshwater, you'll have around 25% normal seawater, i.e., SG 1.005 at 25 C. That's fine for most brackish water fish.
Provided each water change is done with something along these lines, one part seawater to three parts freshwater, any slight discrepancy in specific gravity (or salinity) won't be enough to cause harm to your fish or filter.>
Thank you and have a nice day!
Ben
<Welcome! Neale.>

Re: Echidna rhodochilus, finally      11/1/17 Good day Neale, <Hi Ben!> Yesterday I have mixed approx 1000 ml of seawater, taken from the beach of Jakarta, to the Echidna aquarium. I also decided to take out the ugly white pipe and replace it with two shorter, darker pipes, which matches my aquarium better. Echidna seems to like it better, as he seem to enjoy chasing shrimps round and round the two pipes. <No doubt. PVC pipes are fine, but they do reflect light unnaturally. Can work nicely once covered with a bit of algae though, or if buried in coral rubble.> After the seawater addition, Echidna still behaves more or less before, except for a few changes. I notice that it is now "calmer", not darting around quickly during its "patrols" as often as before. And it seems to leave its cave more often, in favor of the two new pipes. My friend, the one who own a Polyuranodon that I've been trying to buy for years (unsuccessfully), noted that Polyuranodon also behaves more or less the same, if it has more than one hiding places, it will use all of them, not just stuck to one place. Have you observed this with other morays you have seen/kept? <Yes; Morays are definitely territorial, but they are also curious, and in their way, intelligent. Anyone who has kept Freshwater Eels (Anguilla spp.) will have noticed the same thing. These are 'cunning' animals that learn their territories well, and expect to have a 'get-away' burrow or two that they can use if chased or otherwise molested.> Anyway, according to Google, my home in Pulomas Jakarta is only 12 km from the sea. The North Bekasi area where my Echidna were caught, has more or less the same distance from the sea, so maybe our rivers here in Pulomas and North Bekasi are not pure freshwater, but perhaps have some brackish water mixed in. <Possibly, but it may well be that it's plain vanilla freshwater, and the proximity to the sea is more about reproduction, as we've discussed before. Or it could be these fish are casually migratory. By that I mean they simply swim up or down river as the mood takes them, perhaps several times a year. Adult Scats, for example, certainly do this, and can be found 50 km inland, even though they are more common in the sea or estuaries. The truth is that we don't really know very much about how brackish water fish live. They are not well studied by scientists, and fishkeepers are not as experienced with them as reef fish or rainforest fish. People keeping freshwater Morays are doing groundbreaking stuff here, and it's useful to keep notes and discuss with other fishkeepers.> I'd love to check their salinity once I get my hands on a proper Hydrometer. <And I'd love to hear what you learn!> If it's true, that explains how my friend is able to keep Polyuranodon for years simply by using the water from the river, no marine salt required. <Quite so.> Thank you for pointing me to Fishbase and the scientific paper. I also find your interesting comment in this forum: http://www.fishforums.net/threads/identify-my-brackish-moray-eel.105762/ <Oh! That's going back a while.> You said: "...Gymnothorax polyuranodon for example is said to be a catadromous species, that is, while adults may inhabit brackish or fresh waters for extended periods, they return to the sea to breed. This agrees with Schafer's records of these fish being found 'a long way upstream in completely fresh water'....Gymnothorax tile on the other hand is *suggested* to be anadromous, meaning that it inhabits brackish and marine waters as an adult but breeds in brackish or fresh water....Echidna rhodochilus isn't referred to as either, so by implication may be euryhaline, swimming and breeding wherever it wants..." <Hmm...> I found it so fascinating. So, there are not much scientific info about Echidna Rhodochilus? <Not really, no. If you Google 'Echidna rhodochilus' you will get some links, including a first report of the species from mangroves of the Andaman & Nicobar Islands, which is cool. I do suspect they're simply plain vanilla euryhaline brackish water Morays, rather than true freshwater species, as might be the case for (adult) Gymnothorax polyuranodon.> That's too bad. I hope my observations here on my own aquarium will help to shed some lights on this fascinating fish. <As do I.> I also hope that someday people would find a way to breed Echidna Rhodochilus. I think it's the ideal pet moray. It stays small, not so aggressive, it's freshwater to brackish, it's very cute and it has long live if taken care properly. <It does seem to be a very good aquarium fish, given the right conditions. Some of the smaller marine Morays have a well-earned place as rock-solid aquarium residents, and with a bit of care, Echidna rhodochilus would seem to be much the same sort of fish. Healthy specimens are really gorgeous, with a lovely velvety sheen, and as you say, they're relatively mellow -- though I wouldn't trust them with small or delicate tankmates.> Well, have a nice day and thank you again for your wonderful discussions, you're very kind & a true expert of this field! <Thanks for the kind words.> Best Regards, Ben <Cheers, Neale.>

Re: Echidna rhodochilus, finally    11/3/17
Hello Neale,
<Ben,>
Thank you for your advice about the PVC pipe. Tonight I took out Echidna's cave and replaced the PVC pipe back in. I noticed that the cave has rough edges and I am afraid Echidna will scrape and hurt itself on those edges.
<Can certainly be a risk, but these eels do inhabit oyster reefs and mangroves, so probably have some common sense here. Nonetheless, "safety first" is a good maxim!>
Here is a clip of my lovely Echidna before I took out its cave. I hope it will forgive me. My friend told me that Echidna Rhodhocilus are not as easily stressed as other morays, is that true?
<Probably; they are physiologically adaptable, that is sure. Morays are hardy anyway, and among the tougher marine fish, so a euryhaline one is likely to be remarkably durable. The flip side though is that they've been
abused a bit over the years, kept in freshwater systems for too long, and surely some have died prematurely because of that. We don't really know that much about their diet and reproduction either, so might be missing
important things in those directions.>
https://www.youtube.com/watch?v=McgRWm92xN8
<Nice!>
I am fascinated with your info that it is us, Freshwater Moray keepers, who are leading the (informal) research on FW moray behavior. I want to share this video clip with you, sent to me by my friend who keep several Polyuranodons.... in "FRESHWATER" for years ("Freshwater" because I he said he just fill his aquarium with the water from the river where he caught the eels, but I never ran a salinity check on those waters).....and after
years, he was able to train his Polyuranodons to eat BLOODWORMS... Isn't it amazing? Here is the clip:
https://www.youtube.com/watch?v=816Z5mD9NDs
<Likely a major source of nutrition in the wild. Mosquito larvae are very common -- and very important -- parts of the freshwater food chain. They are also common in brackish water habitats too.>
Now you can put it on your notes, that there is a prove case from Indonesia, of Polyuranodons actually kept in "freshwater" for years and trained to eat bloodworms!
<Your messages are shared with everyone who reads WWM, whether now or in the future!>
Off course, we have to take into account that this is Indonesia, the natural habitat of these eels, and they are being kept in the water from their own rivers, and the surrounding temperature is pretty much the same
(they are literally being kept in a city of the same island where they were taken from). Therefore this should not be interpreted that I am advising fish lovers in other countries (especially Western!) to start keeping Polyuranodon on freshwater and feed them bloodworms, I don't! Because what works here in Indonesia might not work in other places.
<Quite so. Your specimens have endured less handling and shipping -- it can easily be months between capture and ending up in an American or European aquarist's fish tank. That will make a difference.>
Well, thank you for your continuing attention and support!
Best Regards,
Ben
<Always glad to talk. Cheers, Neale.>

Re: Echidna rhodochilus, finally      11/6/17
Hello Neale,
Again, many thanks for your input & continuing support! WetWebMedia is really blessing for all of us fish-lovers everywhere!
<Thanks for the kind words.>
Now I am inspired to train my Echidna to eat bloodworm too. Will post here the results, though I am sure it will take a while. Maybe I will get another Echidna as well, because what's better than one Echidna Rhodochilus? TWO Echidna Rhodochilus! :D
<If they get along, at least...>
I will also try to acquire a G. Polyuranodon for the same purpose. Maybe when I get two Echidnas, I will trade one for a G. Polyuranodon :D
I have thoughts on obtaining a G. Tile, however this species grows big, and I don't have that much space in my current house for another aquarium.
Plus, though it is a known species in this part of Indonesia where I live, G. tile and E. Rhodochilus are harder to find than G. Polyuranodon or even E. Nebulosa.
<Really?>
Getting an FW moray around here is a bit tricky, because these days most of our local fish catchers who supply ornamental fishes for fish shops, does not really understand the taxonomy of the fishes. They use "catch-all"
terms for the fishes, for example, any eel types they caught in the estuarium, they will say "It's a Belut Muara" (estuarian eel), whether it's Gymnothorax Tile or Gymnothorax Undulatus or Echidna Nebulosa or even Gymnothorax javanicus. I have to inspect what they caught, and sort the fishes by myself.
<Interestingly, when I Google the "Belut Muara" name I end up with mostly Synbranchus-type swamp eels, such as Macrotrema caligans. These are brackish-tolerant freshwater fish, more of low-end systems than mid-to-high
salinity systems. Synbranchus eels tend to be extremely aggressive and predatory, so approach with care.>
It's much more effective to buy the fishes from hobbyists who hand-caught their stocks, and know enough taxonomy to identify what they have caught... but then, these hobbyists often developed emotional attachments to their pets & won't sell their favorite ones.
<Indeed.>
Well, this has been a wonderful discussion, I hope it will be useful for WetWebMedia readers & all "FW" moray lovers everywhere.
Thank you & Best Regards,
Ben
<And you; cheers! Neale.>

Re: Echidna rhodochilus, finally     11/15/17 Hello Neale and all you good people in WetWebMedia, <Hello Ben,> As I promised, here is the latest update of my Echidna Rhodochilus. 1. After I raised the salinity by pouring in seawater gradually, I noticed that sand sticks on echidna's slime coat. I thought it was some kind of disease, but when i gently touched the echidna, the sand came off. So I stopped raising the salinity, at the weekly water change I no longer add seawater & did the water change using freshwater from my well. Just a few days after, echidna went back to normal with no more sticking sands. <Quite normal behaviour. Mucous production is one way that scale-less fishes like eels adapt to their environment. It's perfectly normal for them to produce extra mucous at times, and eels of all kinds are famous for doing this. It may well be that salinity changes trigger mucous production, perhaps because it slows down water loss in more saline water.> 2. Echidna Rhodochilus are amongst the smallest of the moray, but they are actually strong enough to rearrange their aquarium. My echidna is able to uproot my bogwood ornament and moving its home pipes around as it sees fit. It is more active now than weeks ago when I first got it. <Again, eels are noted for their strength. Despite their sluggish behaviour during the day time, they are actually effective and powerful predators at night.> 3. It is very docile though, it never made any attempt to bite me whenever I stick my hands inside the aquarium to put the pipes and bogwood back in place. <On the whole Morays are known to be curious rather than aggressive towards people, even wild Morays in the oceans.> 4. Maybe later, I'll temporarily (not long-term, maybe just days) put docile pet fish from my other aquarium to test their compatibility with Echidna in a semi/low-end brackish condition. I have a Monopterus albus which are larger than the Echidna, and whose docility are guaranteed, it has been housed for years with two Polypterus palmas, three clown loaches and two yo-yo loaches, and it never caused trouble. Seems like a perfect candidate for the experiment. Or maybe I put the clown loaches, as they have grown rather big and I am sure echidna won't see them as food. <Does sound like a good candidate for this, but I will caution you that Synbranchids are often reported to bite companion fish, so keep a close eye on things.> And thank you for the tips in selecting caught fish. We never know what got caught by local fish catcher here. Besides aggressive eels. sometimes even marine food-fish like ikan layur/ribbon fish (Trichiurus lepturus) end up in estuarium and get caught. Those fishes has nasty teeth! <What a cool beast! One of the neatest fish I've seen in aquarium shops in England is another eel, Congresox talabonoides, sometimes called the Pike Conger Eel. It's a brackish to marine fish, and seems quite hardy and peaceful. But it is predatory, and apparently sometimes reaches over 200 cm in length!> Best Regards, Ben <Thanks for the photos. Cheers, Neale.>