Freshwater Moray Page

My Experiences in keeping 
Freshwater & Brackish water Morays 

By Ben Haryo

(C) 2017-2018 Ben Haryo

(Updated June 6th 2018)

Above: Left - Echidna Rhodochilus, Right - Gymnothorax Polyuranodon, in my aquarium.
Below: Echidna Rhodochilus "Mr. Emerson", my largest eel

Above: Gymnothorax Polyuranodon "Mr. Poly" AKA Tiger Eel, my recent acquisition (Christmas 2017).

This is "Mr. Emerson", my largest Echidna Rhodochilus, size 40 centimeters. 

(All Pictures in this site (c) 2017-2018 Ben Haryo 
unless otherwise noted)

This page is dedicated to my research into Freshwater Moray Eels from Indonesia, especially Echidna Rhodochilus (the White-Cheeked Freshwater Moray Eel AKA the Pink-Lipped Freshwater Moray Eel), and other Freshwater & Brackish moray species which could be found in this country.

Are they really "Freshwater" ?

There are lots of debates regarding the "Freshwater" status of certain Muraenid fishes. 
Indeed, mentioned Echidna Rhodochilus (the "White-Cheeked" Moray or "Pink Lipped Moray"), Gymnothorax Polyuranodon ("Tiger Eel") and Gymnothorax Tile (the "Freshwater Moray") as capable of living in freshwater.


On the other hand, the prominent site WebWebMedia (of which I am a follower for years), and many other sites, cautioned that these eels are "freshwater" in name only, and are best kept in brackish and marine, for good reasons, as there are lots of reports of these eels refusing to eat and/or got hit by various diseases when kept in a fully freshwater environment.

References: (Very Good Article about FW Moray Eels by Mr. Marco Lichtenberger) (Another Good Article about FW Moray Eels by Mr. Bob Fenner) 

I live in Indonesia, and here the experiences of FW Moray keepers are vastly different with what has been experienced in another countries. I have witnessed and know by my personal experiences, that many fish keepers here in Indonesia does keep Gymnothorax Polyuranodon and Echidna Rhodochilus in freshwater for years with no ill-effects. Gymnothorax Polyuranodon kept for years in freshwater with freshwater stingray, in Bekasi, Indonesia, and has been trained to eat bloodworms. The owner of this Echidna Rhodochilus kept this eel for almost a year in freshwater with an Oscar. I bought this eel to save it from the Oscar.. because I don't trust an Oscar with such a small eel. 

So, the mystery is, why these FW Morays are doing fine in freshwater in Indonesia, while dying in other countries when not kept in marine or brackish water?

UPDATE 29th of December 2017: Other than E. Rhodochilus , G. Polyuranodon and G. Tile, there are other species of morays which frequently caught in Indonesia's rivers. These species will have their own descriptions soon. Amongst them are Strophidon Sathete, the Slender Moray, which could grow into 4 meters.

The bucket below is filled with morays captured from a rivermouth at the north of Java island. It contains babies of marine morays such as Echidna Nebulosa, Uropterygius Micropterus, Gymnothorax Richardsonii and Gymnothorax Pictis. 

These are supposed to be marine morays, but the fact is that their babies are being caught in brackish/fresh water of our rivers. This will require further investigation.

It is interesting to note that the Gymnothorax Richardsonii is known as a delicacy in the Phillipines. They call these eels "Bakasi" & considered as a special dish from Cebu.

I also have discovered (anectodal) evidence that Echidna Nebulosa could survive for years in mid-brackish water 1.012-1.014, a friend of mine, Mr. Eko, happened to keep one E. Nebulosa for 2 years. It was captured in brackish water  (estuarium) and kept in the same kind of water. However this is certainly not an optimal way to care for E. Nebulosa & not recommended.

ABOVE: Mr. Eko's Echidna Nebulosa in a brackish tank.

More about Echidna Nebulosa below!

SPECIAL UPDATE (June 6th 2018)

I found a scientific report by Japanese scientists in Yonaguni Island, Okinawa. This report were published in 2016 so it's still fairly recent. They confirmed that Gymnothorax Richardsonii and Uropterygius Micropterus are indeed found in brackish rivers in the Yonaguni Island. U. Micropterus in Tabaru river, and G. Richardsonii in Kubura river. They also, surprise!, found E. Nebulosa in Tabaru river. 

So, these findings are consistent with my own findings that those moray types also visited brackish water, and in case of G. Richardsonii and U. Micropterus, we have reasons to believe that they are indeed marine to brackish species. 

Intermezzo: Meet my White Cheeked Eels

These are my first Moray Eels, all Echidna Rhodochiluses, that I keep at home, in a semi-brackish aquarium. I fluctuate the salinity by alternating the weekly water changes; sometimes I put one part seawater and four parts freshwater, sometimes I put no seawater at all. So far these eels are healthy and playful, no ill-effects observable. They are eating live river shrimps, guppies and sailfin mollies. I am not yet weaning them away from live food, as it's a lot of fun watching them chasing and terrorizing their prey ;) 

This is a clip of my very first Echidna, it is the smallest of my morays. I bought the others several weeks after him. He has been kept for a year in freshwater by the previous owner. 

To this day (27th of December 2017), I am able to entice Mr. Emerson and Mr. Wakeman to eat frozen shrimps.
. However, the smallest one (Mr. Echidna) still prefer to eat feeder shrimps & guppies & mollies.

Here are two videoclips of Mr. Emerson eating frozen shrimps.

In Christmas 2017, I got a wonderful Christmas present, a lovely 35 cm Gymnothorax Polyuranodon. 

Left: Gymnothorax Polyuranodon. Right: Echidna Rhodochilus and Gymnothorax Polyuranodon. Despite being smaller, the G. Polyuranodon are not intimidated by the larger Echidna, and the Echidna does not consider the smaller G. Polyuranodon as a "threat".

UPDATED (4th of February 2018): Gymnothorax Polyuranodon now eating bloodworms in addition to live food.

UPDATED (4th of January 2018): Several days ago i acquired a small brackish moray from a friend, it is not a common moray (not G. Tile, not G. Polyuranodon, not E. Rhodochilus). Interestingly, it adapt to my aquarium much quicker than the other morays. In less than a week it already willing to eat frozen shrimp.

BELOW: close up of my small moray.

I think this small mistery moray is either an Uropterygius Micropterus (small fin tidepool moray) or a Gymnothorax Richardsonii (also known as "Bakasi", a delicacy in the Phillipines). Both species are found in the estuary and in the shallow waters near the beach.

UPDATED Jan 11st 2018: I conclude that my mystery moray is an Uropterygius Micropterus, as closer inspection revealed that this moray's dorsal fin does not start at the back (above the gill openings), but farther down near the tail. Thank you Mr. Marco Lichtenberger for the identification.

UPDATED March 3rd 2018: I have to give away my Uropterygius Micropterus to a friend. It lived well in my aquarium & no problem with my salinity of 1.008 sg, but lately I noticed that Uropterygius is too slow & sluggish compared to other morays. It keeps on losing its lunch, "robbed" by other, faster morays. This means that U. Micropterus are better kept in its own aquarium with no other predators. So, I have to let go, as this species will not survive long in my aquarium where G. Polyuranodon and E. Rhodochilus are much bigger and faster.

This is a video of E. Rhodochilus stole U. Micropterus's meal right under its nose. Notice that U. Micropterus seems to be too slow in finding its food, while E. Rhodochilus found the food right away. 

UPDATED April 2018: Mr. Eko lend me another Uropterygius Micropterus to be acclimatized to 1.008sg. This one seems to be not as sluggish as others, it can get to its food before got stolen by others, so I hope it can be housed rather permanently with other morays.

Salinity Level

People are asking me about my salinity levels, the exact numbers. Well, here it is:

Now Ihave established that my salinity is around 1.008 sg (making it a low-end brackish aquarium), and taking into account my habit of fluctuating the salinity, I think the variable is between 1.006 sg to 1.009 sg. I once got it up to 1.010sg, but after a few water changes it went back to 1.008sg.

Back to our Question

Back to our question. I am baffled by the fact that FW Moray Eels are dying in other countries when put in Freshwater, while it's a common practice in Indonesia to put FW Moray Eels in....well, Freshwater.

WetWebMedia mentioned that Gymnothorax Polyuranodon and Echidna Rhodochilus might be able to survive up to 2 years in freshwater, but the actual lifespan of these eels are actually around 10 years. Thus freshwater keeping, while possible, are not ideal, and these eels need at least brackish aquarium to live out their full potential.

It is worth mentioning that all three FW Moray species (Gymnothorax Polyuranodon, Gymnothorax Tile and Echidna Rhodochilus) are native to Indonesia and neighboring countries. And thus, the stress that is often associated with transporting these eels to other countries are not the case in Indonesia. Which means that the eels that has reached other countries has been weakened in transport. This is one possibility.

Other possibility are individual differences, which are depending on where they are caught. It is possible that these Morays which came from specific places in Indonesia, such as Muaratawar estuarium in North Java, and Segara Anakan lake in South Java, has higher tolerances for freshwater than Morays caught elsewhere. 

There is a minority opinion that many (maybe most) Gymnothorax and Echidna species does have the ability to enter marine, freshwater and brackish water at will, temporarily. It is their adaptability that differs from individual to individual. It is said that a young specimen of moray eel, from a species which are known to tolerate low salinity to FW environment, who entered brackish water and/or freshwater, might develop much higher tolerance for those environments, and might end up living there for extended periods of time.

Therefore, the actual species of the Moray in question also matters a lot. Gymnothorax Tile seems to be the least deserving of the title "Freshwater Moray", and better kept in brackish. However there are exceptions to this, some fishkeepers on the web (links below) and even Mr. Septian himself told me that  it IS possible to keep G. Tile on pure freshwater, as long as the water quality are keep high all the times.

Gymnothorax Polyuranodon are another story altogether, as nearly all people around here who keep them, keep them in total freshwater settings. Echidna Rhodochilus is more rare, I bought three of them totally by coincidence. But as with G. Poly, all Echidna Rhodochiluses that I know around here, are being kept in freshwater. 

On the other hand, Mr. Septian and some other personal friends has been observed to keep all three species (G. Tile, G. Polyuranodon, E. Rhodochilus) in freshwater with no bad effects. It might come down to the skills of the fishkeeper & the individual adaptability of the eels themselves.

So, my temporary conclusion is that I agree with WetWebMedia, that Echidna Rhodochilus might be kept in freshwater, but only known to survive for up to 2-3 years in FW, and thus  better considered as brackish water species & be kept in slightly brackish water. 

G. Tile are not recommended for pure freshwater settings, and better considered as brackish to marine species. 

As for G. Polyuranodon, I personally think they will do well in FW , however perhaps the Indonesian specimens that I have seen and inspect here, has higher tolerances to freshwater, and could be kept as such in Indonesia, though may not have the same tolerance when shipped to other countries.

I am also experimenting on keeping morays caught in brackish water in.... brackish water aquarium (1.008 sg) :) I will report my observations here.

UPDATE: MAY 31st 2018

Last month, Mr. Eko contacted me and told me that he found another Echidna Nebulosa in the same brackish river where he caught his. So I got the eel and decide to try to keep it in brackish, as a matter of experiment.

I was rather apprehensive at first, I have heard stories of morays refusing to eat in aquarium, but this particular E. Nebulosa has been eating voraciously since DAY ONE... In fact its appetite seems to be bigger than my other eels!

It also gets along with other morays, as far as my observations goes. It even hides itself under the big body of Mr. Emerson :D 

So far the Nebulosa seems happy and content in my aquarium, it is my most active eel and also the most gluttonous! :D 

So I will temporarily keep this eel (I call it Eyal) in my aquarium, and i will rehouse it to SW or return it to the river, if Eyal seems to be stressed.

Opinions Around The Web About 'Freshwater' status of Freshwater morays

A Scientific Journal, published by Griffith University, contained an article about G. Polyuranodon, and the conclusion by the author, Mr. Brendan Ebner, is that this species is capable of surviving and growing substantially in freshwater. This finding combined with an increasing number of exclusively riverine based observations of adult G. polyuranodon in the field lends significant support to the idea that G. polyuranodon may actually be a long-term riverine inhabitant in the adult phase. This was published in 2017 (last year) and thus I believe this is the most correct & updated version of the information we have thus far.

A writer named "Kazie" from reported that he has kept Gymnothorax Tile in freshwater for 2 years with no problems at all.

William Berg from Aquatic Community dot com has this to say "...these fishes are not really freshwater fishes, even if they can be found from time to time in freshwater. They are much rather kept in brackish waters. This said I should add that it is possible to keep these fishes in freshwater more permanently, however the fishes are much more sensitive in freshwater and therefore this is not recommended if you don’t have extensive experiences with these species and even then brackish water is preferred.."

A Scientific Paper by Tsukamoto Katsumi et al about Gymnothorax Polyuranodon in Fiji suggests that G. Polyuranodon is a true freshwater species. 

In this Indonesian Discussion Forum "Kaskus", people who fished Echidna Rhodochilus and Gymnothorax Polyuranodon out of the river discusses about their catch, and an experienced aquarist named MedicineMan suggest that they keep the eels in freshwater which are infused with marine salt until reached the SG of 1.005 to 1010.

Aquariumglaser fish importer from Germany described G. Polyuranodon as a true freshwater moray species, that is, "freshwater-tolerant" but spawns in the ocean.

This writer with the forum name "Aquarian" from the Tips.Fm forum has the same general idea with me. He mentioned that Echidna Rhodochilus can be kept in freshwater, brackish water and seawater, however he keep his own E. Rhodochilus in brackish water settings of 1.008 salinity.

Here, "Aquarian" shares his/her experiences keeping Gymnothorax Tile. Interestingly, he/she mentioned the importance of ensuring that the fish are "settled down" in the new home. He/she also mentioned that he/she had kept G. Tile in bracksh and freshwater with no notable differences.

A person in Yahoo! Answers noted that G. Tile (he termed the eel "Indian Mud Moray") could live in freshwater, but he recommend brackish water of 1.008 salinity.

Another writer from wrote about eels in general and mentioned freshwater morays, of whom he recommends several degrees of salinities for each. 

In there was a debate about whether "Freshwater Morays" actually exists. 

A scientific paper from Australia suggests that adult Gymnothorax Polyuranodon are true freshwater fish.

A scientific paper (in Bahasa Indonesia) which describes a population of Gymnothorax Polyuranodon in an inland river in the Island of Sulawesi (Celebes). It also described how volatile these eels are, as only 3 of the samples collected survived the transport back to Jakarta, and all of these 3 eels died within a week (presumably due to being weakened during transport).

Overall, there are lots of opinions about these eels, and it is hard to form a conclusion. My own personal conclusion is that each eel are unique creature & each has their own preferences whether freshwater or brackish. It is very possible that transportation trauma hurts these fishes & lessen the chances of their longevity in freshwater. On the other hand, some individuals from specific population that were caught in certain places in Indonesia (and maybe also other places) has developed larger tolerance to freshwater & could theoretically live for years in freshwater. Again this is not recommended; even if an aquarist is intended to keep the fish in freshwater, it is very advisable to at least add some seawater in the aquarium.

If you find a "Freshwater" Moray, you can try to keep it in freshwater, but be prepared to move it to a brackish water settings if it displays some symptoms of "not quite compatible with freshwater", such as: refusing to eat, or getting hit by various diseases.

Other Observations

Morays has very bad reputation for being vicious, aggressive fishes that will bite humans & are not sociable with each others. My experience with my Echidna Rhodochiluses, however, proved differently. 

Indeed, they never attempted to bite me when I am putting my hands in the aquarium for routine maintenance. They even swim around my fingers on many occasions, as if swimming around mangrove roots. 

As for not being "sociable", in my aquarium they proved to be very docile and peaceful, they also share their home-pipe together with no fighting at all. This is a clip of my eels sleeping together in their home-pipe.

With that being said, I don't recommend anyone else to "test" the Moray, as all Morays possesses dangerous teeth! 

I also recommend all Moray keepers to exercise caution, including when deciding to keep more than one Moray in one aquarium, as there are no guarantee that they will be sociable with each other. 

My Morays are sociable with each other through their own good will. I put several "homes" in my aquarium for them, but for reasons only known to themselves, they prefer to live together in one home-pipe, so that was their own choice, not mine.

Pictures of Moray Eels commonly captured in our Rivers

(Note: These Moray eels below are mostly captured from the rivers and estuariums in Yogyakarta area. These pictures below courtesy of Mr. Septian from Yogyakarta)

Strophidon Sathete (Slender Moray) on top & Gymnothorax Tile on bottom. .

Another Strophidon Sathete with Pangasius. 

Gymnothorax Tile on bottom, Cichlid on top

Gymnothorax Polyuranodon with Channa and Catfish

close up of another Gymnothorax Polyuranodon. Locals here call them "belut macan" or "tiger eels".

An interesting G. Tile with different skin pattern.

Several unsorted & unindentified Moray Eels caught in a river in Yogyakarta. At a glance looks like U. Micropterus, G. Flavimarginatus & G. Fimbriatus.

Close up of one of the unidentified morays above. We think it's a snake moray.

Another close-up of the unidentified Moray above. Very nice texture. It might be an Uropterygius (snake moray) species, considering lack of visible dorsal fin.

What Fishbase said?

Besides the usual suspects of Echidna Rhodochilus, Gymnothorax Polyuranodon and Gymnothorax Tile,, to our surprise, listed a lot of other moray species which are known to live in brackish water. Which means they are marine species that sometimes venture to brackish and maybe even freshwater. This does not guarantee that all of them could be kept in brackish water or freshwater for a long time. Below are some of the morays that Fishbase mentioned as being capable of entering and living in brackish water:

Uropterygius Micropterus (tidepool snake moray) -> this one has been proven to life comfortably in 1.005-1.008 sg low-end/semi brackish aquarium. Probably even freshwater, according to anecdotal evidence from Mr. Septian from Indonesia. I recommend this moray for beginning brackish aquarists, as it does not grow big (30cm max), not so shy and not fussy eater. 
Strophidon Sathete (Giant Slender Moray) -> this one has been successfully kept in freshwater by Mr. Septian from Indonesia. But totally not recommended because they do grow very big, up to 300cm maybe more.
Gymnothorax Fimbriatus (fimbriated moray)-> this one is usually considered as marine, but has been captured in freshwater as well. Better considered brackish. A fierce moray which are not really recommended for beginners or community aquarium.
Gymnothorax Ruepelliae (banded moray).
Gymnothorax Undulatus (undulated moray)-> this one are known to enter rivers, but not recommended as pets, as it is rather fierce.
Gymnothorax Pictus (painted moray)-> Mr. Lilik from Indonesia reported that these frequently caught and kept in freshwater. But not recommended for beginner as the grow big & better considered as marine species. 
Gymnothorax Meleagris (turkey moray)->I actually witnessed these captured from a river in North Java, Indonesia. Fishbase mentioned that G. Meleagris is a marine, freshwater and brackish species. I declined to buy it because it could grow very large. Nevertheless, here we have another confirmed freshwater species of moray, which are unfortunately not recommended for aquarium keeping.
Gymnothorax Favagineus (laced moray)-> these are very familiar in aquarium trade in Indonesia, and has been caught both in the coral reefs and in estuarium.
Echidna Leucotaenia (whitefaced moray) -> these are very similar to Echidna Rhodochilus, and also capable of living in freshwater. It could grow a bit larger than E. Rhodochilus.

Special mention: Gymnothorax Afer. This species are unique to Africa and Atlantic Coast, so not likely to appear in Indonesia, However I mention this species because this is the only one which Fishbase mentioned as brackish water and amphidromous. 

Echidna Nebulosa?

Fishbase said E. Nebulosa is a fully marine species, and I agree. For most aquarists, it is much better to keep E. Nebulosa in a saltwater aquarium, other type of water (BW/FW) not recommended.

However, we do have anecdotal evidence, both in real life and in some articles, about E. Nebulosa being found in brackish in the wild.

Let me quote: "...Snowflake eels are native to the Indo-Pacific Ocean all the way to Hawaii, as well as Baja California and Mexico. In the wild, they can grow as large as 40” (102cm). They tend to reside in rocky crevices and reefs, where they wait to ambush fish and other small sea creatures. It is one of around 120 species of marine eels. They tend to prefer more brackish water in the wild and are more peaceable than other eel types. They become most aggressive when feeding....."

The Encyclopedia of Life, in fact, mentioned that E. Nebulosa is also found in brackish estuary and mangrove, which is consistent with our findings here. 

Fishbase actually mentioned that E. Nebulosa are caught in brackish in Tanzania.

This off course does not mean that I recommend to keep E. Nebulosa in brackish. Please do not reproduce my experiment. Or, if you really do try to keep E. Nebulosa in brackish like I do, please do it only temporarily, and rehouse/re acclimatize the eel to an SW setup at the first sign of distress.

Final Thoughts

This article page is a work-in-progress, that is, I will update it when I receive more info. As for now (January 2018) my focus is still on E. Rhodochilus and G. Polyuranodon, however when I can obtain a Gymnothorax Tile, I will do the same with that one as well. I will also update this article when I am able to obtain marine morays that actually could live in brackish water.

Thank you for your kind attention, and I appreciate any comments. Please send your comments to my e-mail ben.haryo (AT) 

Very special thanks for Mr. Neale Monks, Mr. Bob Fenner & Mr. Marco Lichtenberger of WetWebMedia for their insights about FW Morays and aquarium fishes in general.