FAQs about "Freshwater" Morays Eel
FW Moray ID, FW Moray Behavior, FW Moray Compatibility, FW Moray Systems, FW Moray Feeding, FW Moray Disease, FW Moray Reproduction,
Marine Moray Eels,
Related Articles: Freshwater Moray Eels by Marco
Lichtenberger, Freshwater Moray
Eels, Moray Eels, Other Marine Eels,
Re: bumblebee grouper in freshwater? Plus now, FW Moray
Thank you for the detailed and fascinating reply.
I understand your explanation. We Indonesians are blessed to live in the
tropics; and many of our native fishes which are "common animal" for us, are
often "luxury pets" for people in another part of the world.
People in Europe and USA would have to be more careful in choosing the best
tropical fishes for their system, and ensuring that they buy only the animals
which are compatible with the aquariums they have. Otherwise, it's
money wasted, and precious live fish wasted :(
<Quite so. If you're experimenting with a common brackish water fish, one that
would just as likely end up on a dinner plate, then seeing how it would do in a
freshwater tank is understandable. Of course nobody wants to
kill a fish slowly across weeks or months, so if the fish stops eating or starts
getting sickly, then switch it back to brackish water conditions.
But if it's fine, then I don't see the harm.>
And certainly any fish that could grow bigger than one meter, like those poor
groupers, are not ideal pets :( better let them swim free in the ocean..
<In this case, yes, probably best.>
It is fascinating to read that individual variations does matter in the survival
of brackish/marine species in freshwater.
<Among all species, actually. Just think about humans -- all one species, but
with very slight variations that make individuals better at handling different
levels of UV exposure, oxygen availability, ability to digest milk as adults,
ability to resist diseases like cystic fibrosis and malaria -- all sorts of
minor genetic changes that evolution can work with. Nothing big enough to stop
us all being humans, but things that mean a person well suited to one part of
the world would be less well suited to another. This is the golden rule of
biology -- the more variation, the better it is for the species. Doesn't matter
if you're a human or a fish!>
As a matter of fact, I know a fish enthusiast who kept Gymnothorax
Polyuranodon in freshwater for many years, with no apparent bad effects to the
eel (I tried to buy it from him many times, never succeeded). He did
not buy the eel from a fish shop, he bought it directly from a fisherman who
fished the eel out of a river in Cilacap, South Java.
<There may well be regional populations of this Moray better adapted to living
in freshwater. But if the ones traded internationally are from estuaries near
the big cities, then those are the ones aquarists in Europe and the US will have
to deal with. This is known for some Archerfish species, including species
ordinarily thought of as brackish water fish known to breed at sea, but in some
cases with landlocked populations that clearly don't do this. Because those
landlocked populations are never traded, the standard advice to keep Toxotes
jaculatrix and T. chatareus in brackish water aquaria is good advice -- unless
of course you happen to live local to a true freshwater population and can
collect them yourself!>
Perhaps this is a case of a lucky eel, because I read in the web, sad stories of
morays who became stressed (some even died) after being kept in freshwater.
<Indeed; they commonly stop feeding, and after a few weeks or months, just die.>
I attach the picture of his eel with this picture.
<Do I see an Anabas climbing perch in there? Neat fish; never had the chance to
keep one, but on my wish list!>
He mentioned that he does not use any chemical formula, not even marine salt, he
just put the eel in the aquarium (together with some Anguilla bicolors), and use
the water taken from a nearby river, mixed with tap water.
<Not so easy if you live in England!>
Well, again thank you for the discussion, and I wish you a wonderful weekend!
<Thanks for writing and sharing these photos. Cheers, Neale.>
I recently bought a marble moray eel ("freshwater)
who seemed to be doing great until I found it dead today
<Quite common; most specimens are "lost mysteriously". Not an "aquarium
All water conditions are perfect, the tank has been up for a little
under a year, and I have a great deal of salt in the water since they
are brackish creatures. She didn't stop eating, she wasn't having
labored "breathing", and her color was beautiful. I found her belly up
on the floor, and her stomach seemed to have been opened with lots of
attached little beads hanging out. Any idea of what could have happened?
and the linked files above. Bob Fenner>
Compatible eels... BR 1/24/11
How are you?
<Just fine, thanks!>
I'm looking into adding an eel into my 55 gallon tank. Right now I
have a pair of monos.
<Which need brackish water now, and preferably saltwater once
mature, limiting your options.>
I do plan on getting a few more of them and maybe a few more different
type of fish.
<Monos will outgrow 55 gallons pretty quickly; you really need 150+
gallons to get the best from them. They can be aggressive towards one
another, and in small groups sometimes the biggest one becomes a bully.
Be careful. Read up on the needs of Monodactylus argenteus
I would like to know which eel would be the best fit.
<None, really. While a Fire Eel or Tyre Track eel might work in a
low salinity system, up to SG 1.005 at 25 C/77 F, this won't be an
ideal combination because of the Monos. The so-called Freshwater Morays
are of course brackish to marine species, and while suitable for big
brackish water tanks with Monos, the reality is that some Morays become
"snappy" and cause problems. Echidna rhodochilus is perhaps
the best bet because it feeds mostly on invertebrates, but Gymnothorax
tile is the most commonly traded Moray and is a fish-eater, so that bit
more likely to cause problems.>
My pH is at 7.6 and I have it set up with a lot of rocks and caves and
some fake plants. Maybe an eel isn't a good idea?
<This is usually true.>
And also if you guys could tell me a few types of fish that would mix
well in these conditions. I was told some freshwater puffers
<None of the freshwater puffers is suitable for mixed species
set-ups, with the possible exception of the South American
and maybe a clown knife?
<Can't be kept in brackish or salt water, so not suitable for
life with Monos.>
<Hope this clears things up for you! Cheers, Neale.>
Re: Compatible eels 1/24/11
The monos I purchased are the ones with the black stripes.
<Monodactylus sebae, also known as the West African Mono.>
Are they the same as the yellow fin ones?
<In terms of care, yes, exactly the same. They do get bigger, or at
least deeper, so you need a very deep aquarium for them. Adults are
typically 20 cm/8 inches deep, so your tank will need to be at least 60
cm/24 inches deep.>
Well what would be a good mix with these fish at the pH 7.6?
<pH isn't the issue; salinity is. These Monos need brackish to
marine conditions, SG 1.005 to 1.025. The ideal is probably around SG
1.010 at 25C/77F. Assuming you're using marine salt mix at an
appropriate amount (about nine grammes per litre for SG 1.005 at 25C)
then the pH should automatically set at around 8. So choose companions
that need the same middling brackish or marine conditions. Most people
keep their Monos either with hardy brackish water species -- Mollies,
Scats, Archerfish -- or else with robust marine species such as
Damselfish, Surgeonfish and Lionfish. At higher salinities you can also
use a skimmer, and this does seem to improve Mono health; Monos come
from the highly oxygenated surf zone part of the sea, and they dislike
old, stale water. Monos kept in freshwater rarely do well for long, and
tend to be prone to diseases such as Pop-eye and Fungus.
Do read about them on my Brackish FAQ or in my book:
Re: Compatible eels 1/26/11
Ok thank you. All I have done so far is add aquarium salt
<Marine aquarium salt. Not "aquarium salt" or "tonic
salt". If it isn't what you use in a marine aquarium, it
won't do in the long term.>
as required for a 55 gallon tank. The monos seem to be doing fine.
<Yes, they are hardy, at least when young. Above a certain size they
do become very easy to kill. Look for nervousness and/or turning black.
These are warning signs!>
I don't know anything about salinity
<Much here at WWM.>
and I'm very new to cichlids
<Monos aren't cichlids.>
and I want to do the best possible. Right now I'm feeding them
Freeze dried bloodworms and I do have some frozen ones for when I have
a more populated tank.
<Will need a more varied diet than this. A good staple is Hikari
Cichlid Gold. Augment with bloodworms, chopped seafood, and especially
strips of tilapia fillet.>
I have a friend that has a tank full of African cichlids.
<Do you mean Mbuna? The rock-dwelling cichlids of Lake Malawi? Far
more types of cichlid in Africa than just these!>
I think they are all peacocks and zebras or something, and one of them
was killed but the other seems to be doing fine.
<What's happened is very common. Pseudotropheus zebra cannot be
kept with Aulonocara (i.e., Peacock cichlids). Pseudotropheus zebra is
a Mbuna cichlid, a very aggressive and territorial rock-dwelling
Aulonocara spp. live more in the open and they are MUCH less
Are these fish something I can consider adding to my tank?
<No. Salt causes Malawi Bloat for one thing. Look instead at Scats
or Archerfish, or perhaps even Giant Sailfin Mollies. If your retailer
can get them, Black-chin Tilapia would also work, as would Green
Chromides (Etroplus suratensis), both of these being brackish water
cichlids and very interesting fish at that. Black-chin Tilapia for
example are paternal mouthbrooders, something very rare among
And food wise, I also have Hikari pellets and I was thinking about
mixing everything together.
<Hikari pellets are a very good food for Monos.>
Sorry to be a pain but am I doing everything good so far?
<Seem to be doing mostly okay, but read, learn, and ask questions!
Re: Compatible eels, BR 1/27/11
Ok so if I already added aquarium salt,
<Which will fine for now. But once the box runs out, switch to
marine aquarium salt mix.>
and I buy marine salt, should I do a water change first or what is the
right process of getting the right salt in the tank?
<No need. Just switch to marine aquarium salt mix as/when the
aquarium salt is used up. Aquarium salt is poisonous or anything like
that. It just doesn't work particularly well, and in the long term
will not be good
enough. But for a few months, it won't do any harm.>
Also, how about live brine shrimp? At the store I get them I think they
are in salt water. I'm always told to rinse first before adding
them to my freshwater community tank. Would this be a good food option
<Yes, will be fine for Monos, and no, you won't need to rinse it
off. Just pour the whole package, salty water included, into the
brackish water aquarium. Cheers, Neale.>
Re: Compatible eels 1/27/11
Also I'm sorry I didn't explain in detail about my friends
tank. He bought 2 mono sebae and one was killed
<By the Mbuna.>
and the other is doing fine.
<For now. Will eventually be either killed by the Mbuna or die from
sickness because it's being maintained in freshwater. Monodactylus
sebae needs brackish to marine conditions. It has no place in a Rift
He has those rock dwelling cichlids.
<They're called Mbuna. Cheers, Neale.>
Re: Compatible eels 1/27/11
Neale thanks a lot for all your help I know I asked you this before but
if you could point me in the direction of some fish that would be nice
in the tank I'd appreciate it. Not sure if invertebrates would work
but I'm up for anything or any type. Thanks again
<Monos will get along with almost anything they can't eat whole.
The question is whether you intend to keep them in brackish or marine.
Classic companions for aquarists into predators are Colombian Shark
Catfish and/or Siamese Tigerfish (though not all are brackish water
species, so check).
If you want something that becomes tame, then try Scats, the Silver
Scat especially being extremely beautiful. The two Mono species traded
mix extremely well, and if anything, mixing them seems to break down
their tendency to become aggressively territorial. Not sure why. Violet
Gobies would make neat "eel-like" fish though their dietary
requirements are quite specific, so do review before purchase. Some of
the big sleeper gobies make good companions as well, including
Dormitator maculatus and Butis butis.
a lot more brackish water species traded than just these, but finding
them may require a bit of effort. Try perusing my Brackish Water FAQ
for some more ideas, and then ask your local retailer what he can get
Under marine (or at least near-marine, SG 1.018+) conditions your list
of tankmates can include Damselfish, Wrasse, Lionfish, Snappers, really
anything of similar size that won't view the Monos as prey. If you
visit public aquaria, you'll see Monos used extremely often as
"dither fish" for giant reef tanks.
Brackish Aquaria Plant and Livestock Questions
Im an owner of an albino African clawed frog, which is tolerant of, and
even thrives in, brackish water.
<Xenopus laevis is indeed tolerant of brackish water, though only up
to a point.>
Once I upgrade its tank size to 30 gallons, I plan on conditioning it
to brackish water. (I dont feel comfortable working with brackish in
its current 10 gallon home.)
<Hmm... I wouldn't set about creating a brackish water aquarium
for Xenopus. It will do much better in plain freshwater.>
I've been wanting to work with brackish water aquaria for quite a while
Anyways, while I was diving into research about what kinds of brackish
tank mates would be suitable, I stumbled across the freshwater moray
eel, which I think would be an ideal fish for me.
<A bad choice.>
(I like smart animals and morays are geniuses of the fish world.)
<Always seemed dumb as posts to me. If you want intelligence,
you're more likely to find it among Puffers, Spiny Eels, and
especially Mormyridae, though these latter are difficult to
Anyways, if I have a few questions about this eel and about a brackish
First of all, what's a typical price range of a FW moray?
<Not much. Here in the UK, the common species Gymnothorax tile goes
for less than Â£10. On the other hand, the much rarer species
Gymnothorax polyuranodon can sell for more than ten times that
Id also like to know something rather odd; how wide and how tall are
their bodies at adulthood?
<Depends on the species, but most get to a body length around 60-90
cm, with the thickness at the chunkiest part being about 2-3
Would it be a good idea to separate them when feeding them so they dont
steal each others food?
<The Xenopus will become dinner, so it's not a combination worth
investigating. Actually, there are other reasons to avoid this pairing.
Firstly, Xenopus prefers much cooler water than tropical fish,
including tropical brackish water fish. Secondly, Xenopus may tolerate
low-end brackish conditions, but "freshwater" Morays
ultimately need at least 50% seawater salinity, around about SG 1.010.
Thirdly, Morays hunt by scent, and they'll bite at anything that
doesn't swim away quickly; fish are a risk, but a frog would be
Last, is green algae tolerant of a brackish environment?
You see, there's an ornamental variety (moss balls) that has really
caught my eye and Id like to use them.
<Cladophora aegagropila does quite well at low-end salinities. Do
But in general the commonly traded plants are not tolerant of the mid
to high salinity Morays ultimately need. Would suggest either choosing
low-end brackish species that would thrive at, say, SG 1.003, and then
choose plants accordingly. Spiny Eels will do well at this salinity,
are much smaller, and also much cleverer than any Moray I've ever
met. At this low salinity there are lots of brackish water gobies,
killifish, etc. that would work well. Having said that, while Spiny
Eels are often healthier in slightly brackish water, they certainly
don't need such conditions to do well. Cheers, Neale.>
Moray growth cycles 7/16/06 I was looking for
information on moray eel growth. I bought a "freshwater"
snowflake eel of the Gymnothorax tile variety that I have placed with
my albino moray which due to information I have researched I am
assuming it is Echidna rhodochilus. The moray "trademark" of
opening and closing its mouth to breathe is not happening with my
albino. The snowflake is breathing in such a manner and I was told by
the owner where I buy my fish food that he was a very beautiful and
healthy moray as I had just bought him from another shop and went to
get some food from my favorite shop on my way home and showed them.
Does anyone know the growth cycles of morays? <Mmm, yes... there are
some very nice/useful graphs/charts of time versus SL (standard length)
for many species available on fishbase.org> I know they are born in
one form called leptocephalus and around 3 yrs. change into elvers. Are
there species of moray that do not breath the same way or do they
eventually over time grow and change into breathing this way? <Mmm,
some "gasp" more than others in general...> They are both
approximately the same length except the snowflake is flat on the sides
with fins to the tail while the albino is more or less round behind the
neck with a tail that comes to a point with no fins which seems closest
to the pics I have seen of the Echidna rhodochilus of the various
morays I have so far researched. <Mmm:
unfortunately this is one of the species that does not have
"Growth" data on FishBase... Rats! Neither is there such
presented for G. tile... These are typically slow growers in the wild
and captive conditions (actually, likely less than one percent live a
year... due to unstable, unsuitable environment mostly). Bob
Re "FW" Moray growth cycles... dead
7/20/06 Thank you for your help but I have some bad news the
snowflake died on me and I am assuming he died of starvation along with
a possible disease. <... not uncommon... You did (finally) read on
WWM re these so-called freshwater eels?> I kept track of the number
of ghost shrimp and guppies accounting for X amount to be eaten by my
albino and still had more than I should have had. I had a butterfly
goby that lived less than 2 weeks and followed similar patterns before
the final event and both had skin the same condition after death. I did
not see either one eat. The goby I have now has been with me a while.
<... this tank is too small... one more time> The albino is a 2nd
chance for me as I bought one prior and it died but due to water
quality as the aquarium was new and not enough bacteria to break down
the nitrate cycle. I tested the water 2 days ago and it tested really
well for very low levels of nitrite <Should be zero, zip,
non-existent> and I have an ammonia sensor that has not rose above
good levels. <I don't like these "sensors"... not
accurate> Is there anything else I need to check for? <...
read...> I am considering getting another snowflake if possible but
am thinking I should wait until I have a much larger tank for the shear
reason that I hear when they are moved they tend to stop eating.
<Bingo> I had this albino eating within a day of getting him, at
least upon visual verification. I feel comfortable with this guy to go
55 then up to larger as the albino is still small and thinner than my
pinky finger and he seems so easygoing that eating will not be one of
his problems. <Still... need more space> I will need 2 large
tanks since the albino is brackish because I also have an ornate Bichir
that is right around 2" <Wow! Tiny> now and want to get a
Ropefish for his tank mate and have recently moved and need to decide
if the 2 large tanks will be placed together or separately. If I leave
things as they are with the 3 fish in my brackish tank and 55 is good I
would have them together but if I need something bigger for the albino
I will have them placed in different places. I am planning on starting
on getting the 1st tank on the successful sale of the old house to have
money to get the best. I appreciate all your help. <Do investigate,
plan before purchasing livestock... Bob Fenner>
brackish/marine moray growth cycles 7/19/06 Thank you have
been a great help so far and I appreciate the quickness of your
response. I have read various recommendations for aquarium sizes for
eels. I have read that for my albino I would be lucky if it made it to
18" and 24" max and for the snowflake it may reach between
24' to 36". What size aquarium would you recommend. <Please
read here: http://www.wetwebmedia.com/FWSubWebIndex/fwmorayeels.htm
and the linked files above> Do you think 55 would be ok with what I
have and maybe adding a catfish? <Mmm... no, not likely a good
mix> I would not mind adding another butterfly goby and bushfish and
maybe if you could recommend some brackish catfish for the clean up
crew for a total of 6 fish and which size would you recommend for
these? The bushfish maybe to only problem because they may become lunch
as they do not get big but the butterfly has venom to protect him. I
know that 10 gallon is way too small especially with the addition of
the snowflake which I happened upon by shear accident and happened to
be not much bigger than my albino except on the sides. I have been
keeping extra tabs on water quality and am using a bio wheel filter
which I can actually witness how good they are. <Read... keep a
close eye on water quality, get a much larger system... Bob
freshwater moray eel help
thank you for the very quick reply I've
found a moray eel called the White-Cheeked Moray Eel or the
Echidna rhodochilus can you please help me find one i live
in Oldsmar florida if their is any shop or website that
delivers quickly please tell me thank you so much for your
help -Connor <Not a freshwater species... did you read where you
were referred? Use your Yellow Page phone directory to call about for
local stores. Bob Fenner>