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FAQs on the Halfbeaks

Related Articles: Halfbeaks, Species, husbandry and breeding by Neale Monks, Halfbeaks, Livebearing Freshwater Fishes, Livebearing Fishes by Bob Fenner, Poeciliids: Guppies, Platies, Swordtails, Mollies by Neale Monks,

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Identification     5/27/19
I have had this top dwelling fresh water fish in my tank for 4 months. It has not grown in size, as promised by the pet store… lol…. I got it to see what size tank I would need in the future, but it has not grown and is happy eating bloodworms. Any thoughts? I thought it looks like a tiny Arowana or needle nose gar, but it has not grown.
Any ideas? It is about 3” long and very thin:
<Platinum Halfbeak is what these are called in the trade. May be Dermogenys siamensis or Dermogenys sumatrana, or even some hybrid between them. Males stay quite small, 3-4 cm, but females do reach a fair size, maybe 7 cm or so. Nice fish, but jumpy, and like all Halfbeaks, can be a bit finicky about food. Not too bothered about water chemistry, but neutral, medium hardness water is probably the idea. Will tolerate slightly brackish water too. Cheers, Neale.>

Platinum Half Beak     5/27/19
Found it! So sorry, I looked all over the website in areas that made sense to me but due to the fact I had no clue what this fish was, I didn’t know where to start and stumbled on to your halfbeak page. Sorry to bother you. :)
<Not a problem! Cheers, Neale.>

Re: Molly Question; now Halfbeaks     4/25/18
That's great news! Thank you!
And if you can stand another question, something just came up this morning.
A friend of mine called me to say he's moving and has to get rid of his tanks and fish (don't know the whole story, but experience suggests I don't want to know), He has two halfbeak fish (I've never heard of them).
<My favourite aquarium fish! Do see here:
Not widely sold, but well worth keeping.>
He calls them Red Line Gold Spot, Hemirhamphodon-tengah (spelling?) and asked if I would take them because they've always been in his brackish tank (though his SG is higher than mine - he said 1.008).
<Interesting he's keeping them in brackish as these are usually considered freshwater fish, often soft water fish at that.>
I told him I'd do some research (mostly to protect the Goby - I don't want him to be out-competed) and get back to him.
<Wise. But theoretically, the two share little in common in terms of swimming level and diet, so unlikely to compete.>
But the research I've turned up so far says these fish are strictly freshwater, not brackish, and the only place I have room for them is my brackish tank. If that's true, then they shouldn't be in his brackish tank and I won't torture them further by keeping them in mine. Is this strictly a freshwater fish?
<I would agree these are freshwater fish. However, halfbeaks are peculiarly sensitive to water chemistry changes. If these have been doing well in the conditions he's got, let's say for the last six months, feeding happily without any sign of ill-health, I'd be tempted to stick with those. Do also be aware that his halfbeaks might be called something by the retailer, but actually are something else. Wrestling Halfbeaks, Dermogenys spp., are euryhaline and will do well in brackish water, perhaps even better than plain freshwater. Then there are the River Halfbeaks, Zenarchopterus spp.,
which while rarely traded, are big fish that thrive in hard freshwater through to fully marine. Hope this helps, Neale.>
Re: Halfbeaks       4/26/18

Ok, after some thought, I decided these fish would be better off with someone much more experienced than I am, so I told him I'm not going to take them and referred him to the store where I get my aquarium supplies.
The man that owns it has been in business there for 35 years, is very experienced, and they have an "orphan tank" so they can take fish that their owners can no longer care for and find them good homes.
<Definitely fish for fairly advanced fishkeepers, that is true. Hopefully he finds a good home. Do you live in a city with an aquarium club? I'd expect these fish to be attractive to such.>
But thank you for the information.
Halfbeaks sound like interesting creatures, just not right for me at this time.
<Quite possibly. While your fish can't talk, I can say for sure they appreciate you taking the time to think carefully about this hobby and acting accordingly. Cheers, Neale.>
Re: Halfbeaks      4/27/18

I'm about 37 miles northwest of Boise, Idaho. The aquarium store I told you about is in Boise and they are the only source for aquarium maintenance services in the state. The man that owns this store provides maintenance
for a great number of restaurants, businesses, and private individuals with very large tanks, and in many cases he provides the fish, tanks, and equipment as well (thus retaining ownership of all). These are also really good people who genuinely care about the animals in their care (that's why they established the orphan tank).
<Sounds most impressive and very reassuring to have such a retailer (relatively) close by.>
I've seen them refuse to sell fish to customers who they suspect will not provide appropriate care, do not have sufficient tank size for the fish they want, or do not have a sufficient skill level to handle the special care some fish require. That's why I recommended my friend take the fish to them.
So I'm confident they'll be in good hands. In fact, I have one of the store's rescued fish. It's a Tinfoil Barb (about 8 inches) that was left to die, among other fish who did not survive, in an abandoned aquarium left behind after the owner was evicted. This lone survivor did not escape unscathed as his dorsal fin and left pectoral fin had rotted off by the time they got to it. But he seems happy and healthy now and I think he's absolutely beautiful!
<Tinfoils are absolutely beautiful fish, in the right sized tank. They aren't easy to house though, and a lot end up being rehomed at zoos and parks. Cheers, Neale.>

Wrestling halfbeaks breeding questions   12/9/16
Hello all,
I recently purchased a group of six wrestling halfbeaks with the goal of eventually breeding them.
They will be put into a 55 gallon low end brackish tank with one violet dragon goby. The SG will be 1.003. My pH is 7.6 and water very hard.
<Sounds fine, though I think the Violet Goby might spook them. See what happens. If well fed, shouldn't be much of a threat otherwise.>
I'm pretty sure I have at least 1 male and possibly 3 or more females. The male is thin through the chest and has red on his dorsal fin. The females are all silver and a bit rounder in the chest. I also ended up with two I'm not sure of. They have rounded chests like the females, but also have a hint of red on their anal fin.
<The "barrel chested" appearance of the females is distinctive, but the safest feature is the anal fin, which should be more or less triangular, compared with the differently shaped (more rectangular) anal fin of the male. Also, males tend to have longer beaks than females, though this isn't obvious in Dermogenys spp. (it's a lot more obvious on Nomorhamphus
They are all between 1 and 1.25 inches in length.
<Still tiny! Adult females are easily twice that, depending on the species.
Males tend to remain weedy little things, but should still get a bit bigger.>
I haven't yet seen any fighting.
<Given space, any fighting is trivial.>
At what age do these fish reach sexual maturity?
<With halfbeaks it's a bit more complicated than this. They probably can get pregnant when about half adult size, but since female Dermogenys species range in size from around 5 cm to maybe 8 cm in length when fully grown, but identifying species is very difficult, it's very difficult to know if a specimen in front of you is anything like half grown! Basically, I'd assume yours are sexually mature now, but they might not be. If they are, the females will become very barrel chested once pregnant.
Unfortunately, one big issue with halfbeaks is that as they age, fertility seems to decline. No idea why, and it might not always happen. But personally, while I've gotten big broods early on, as the females got older, broods got smaller and/or more prone to stillbirths.>
Is there any way to estimate how old they might be now? Is pregnancy 8 weeks like I've read (only one source, so want to confirm).
<I think that's an overestimate to be honest. 3-4 weeks seems more likely, given their adult size.>
Thank you!
<Cheers, Neale.>

Halfbeak Jaw Dislocated? 5/26/10
Hello Crew,
I have a month-old Halfbeak fry (Dermogenys pusilla) that's had its mouth stuck in the open position for a week now (please see attached photos).
This happened after I fed it some crushed algae wafer, I believe one of the pieces was too large.
<Oh dear.>
Is it possible that it has dislocated its jaw?
<Certainly possible.>
It tries very hard to eat, but can only manage tiny amounts of soft, frozen foods.
The poor thing is growing thinner.
<I can well imagine.>
Do you think it would be best to euthanize it, or is there a possibility that this will resolve?
<It's unlikely to resolve itself without intervention. You might try, very gently, to click the upper jaw back down. But fish bones are very delicate, so this has to be done very carefully. Use something padded, like a Q-tip,
to put pressure on the upper jaw rather than anything pointy. You might even use your fingertips, if you feel confident enough.>
My water tests are as follows: 0,0,5. KH:9 GH:13. Ten-gallon fry tank.
Thanks for your help,
<Good luck, Neale.>

Re: Halfbeak Jaw Dislocated? 5/27/10
Hello Neale,
I anesthetized the little Halfbeak with clove oil and tried to push the upper jaw down, however, it would not stay in place, so I went ahead and euthanized it.
<Oh, too bad.>
On a happier note, my female Halfbeak looks ready to give birth again...
<Cool! Halfbeaks are amongst my favourite fish. I have a piece about them in one of the upcoming 'Aquarium Fish' issues, so keep your eyes peeled.>
Thanks so much for your advice.
<No problems. Cheers, Neale.>

Re: Very Sick Black Molly... (RMF? Ever seen this type of prolapsed vent on a Molly?)
Nomorhamphus liemi
Hi Bob,
Images attached. Includes alternative version with the prolapsed vent highlighted and labeled. These are gratis for your use on WWM where relevant.
Cheers, Neale

Re: Very Sick Black Molly... (RMF? Ever seen this type of prolapsed vent on a Molly?) 7/8/09
Hi Bob,
Have sent the images along.
<Have seen. Thank you Neale>
For what it's worth, in the case of this halfbeak, by guess is that hybridisation might be the culprit. Within the genus Nomorhamphus, there's a spectrum of degrees of viviparity, from simply ovoviviparity through egg/embryo cannibalism to proper placental connections. Since they're all a closely related species flock from a single island, I wonder if closely related species can fertilise one another, but as the embryos develop various failing develop if the connection with the mother isn't "just so"?
It's a shame exporters make no effort at all to offer a single species in each batch of fish, and this may further explain the supposed difficulty of breeding halfbeaks in captivity. Cheers, Neale
<Such is both the nature of the trade presently, and the broader nature of humans... We are "fighting" this gradient... Cheers, BobF>

Halfbeak care and purchasing 12/16/08 Hi all! Great website! I've been doing lots of reading here. I currently have a slightly brackish, planted 29 gallon tank with platies, mollies, and a Krib. I was at a local pet store today that sometimes gets a few oddballs and they had one lone halfbeak. It was labeled as a "Celebes Halfbeak" but it looks almost exactly like this picture: http://www.aqua-fish.net/show.php?h=halfbeak1 <That fish appears to be the so-called Silver or Platinum Halfbeak, a species I believe to be Dermogenys siamensis. The Celebes Halfbeak is Nomorhamphus liemi. You can easily distinguish Dermogenys from Nomorhamphus. For a start, Dermogenys halfbeaks are generally smaller and more slender in build. Dermogenys halfbeaks also have longer "beaks". When viewed from above, Dermogenys halfbeaks have semi-transparent "flanges" on either side of the lower jaw, so that there's a scoop-like construction that is presumably used to guide food particles into the mouth. Nomorhamphus halfbeaks lack these flanges, and generally have short, stubby beaks that curl downwards in some species. Nomorhamphus have a stocky body shape, and the females especially are very sturdy-looking. Nomorhamphus also seem to be happier swimming at different levels of the aquarium, even the bottom, whereas Dermogenys rarely go much below the top of the tank.> Straight beak, silver body, red and yellow fins. It's a little over two inches, and the lady who does the fish ordering says she's never seen any with a hooked beak like the actual male Celebese, but yet has seen them breed in the tank. Supposedly he's been eating flakes. I decided to take the little guy home and see how he does. She'll be ordering a few more soon, as well as the flag fish I was hoping to find. <Does sound like Dermogenys siamensis. I have a picture of a male and female on one of my web pages, here: http://homepage.mac.com/nmonks/Projects/halfbeaks.html Scroll about halfway down.> Are there other species that look close to this picture that I should also consider? He's currently loving my thick stand of hornwort so I don't know if I'll be able to get a picture soon. <Yes, they do like floating plants!> What exactly does the andropodium look like? I can't find any pictures on Google and it sounds like it's not as well defined as the gonopodiums of my other livebearers. <Correct; essentially all you will see is that some of the rays in the anal fin are kinked. But don't expect to see anything like the gonopodium of a male livebearer. Regardless, they're quite easy to sex once you compare males and females in the same tank.> I'd like increase my single fish into a properly sexed trio if possible. Or would that require more space than my 29 gallon? Some articles say they're aggressive with each other. <Dermogenys are aggressive, but in your tank I'd get half a dozen and let them sort themselves out. They won't fight to the death if there are plenty of floating plants.> Also, my current feeding regiment includes Spirulina flakes, a color boosting tropical flake, peas, and frozen bloodworms (and livebearer fry, which everyone seems to relish!). Will this be a sufficient diet for the halfbeak, or should I look at adding something else? <Sounds perfect. Algae-based flake is probably essential, as halfbeaks are at least partially herbivorous in the wild. My specimens thoroughly enjoy Hikari Micro Pellets as well.> Also, I'm getting conflicting information on water changes. I currently do weekly 30% water changes. One of the articles recommended changing only 5% at a time. Are halfbeaks really that sensitive or will my current weekly schedule be suitable? I do check the parameters every day or two just in case. Both my tap water and my tank water are pH 7.5 so there wouldn't be a pH change. <Some halfbeaks are sensitive to water chemistry changes, particularly Nomorhamphus. But Dermogenys are generally quite tough, and some species occur across a wide range of water chemistry values. Dermogenys pusilla for example can be found in fresh, brackish and saltwater conditions. Provided you don't expose your fish to extreme, rapid water chemistry changes, they should be fine with the usual 30% water changes you do.> Thanks! Angela <Cheers, Neale.>

Re: Halfbeak, now with pictures 12/16/08 Hello crew! This is Angela, writing from my home email. I emailed you earlier this night from my work email at Pentair Water. My little Halfbeak friend has come out of hiding and allowed me to take a few pictures. Please excuse my poor skill with aquatic photography, I'm much better with furry animals. Side view, colors washed out a little: http://i15.photobucket.com/albums/a371/naturestee/100_6635a.jpg Top view: http://i15.photobucket.com/albums/a371/naturestee/100_6621a.jpg Am I right in thinking this is a Wrestling Halfbeak? <Certainly Dermogenys sp., most likely D. siamensis. To my eye at least, D. pusilla is more greenish rather than the brilliant white-silvery colour of D. siamensis. There's a nice picture of D. siamensis here: http://research.kahaku.go.jp/zoology/Fishes_of_Libong/data/p017_01b.html All Dermogenys are very similar in terms of care, and in my opinion they are the ideal "beginner's halfbeak". They breed readily, but the fry are quite small and easily eaten by other fish, so you're lucky if you find even one or two. Quite possibly worth moving pregnant females to their own quarters, or even a largish breeding net, depending on the size of the female. By contrast Nomorhamphus females are huge (10 cm/4 inches in some cases) and produce enormous fry that easily survive a few hours in well planted tanks, so you've got more chance of catching them and moving them. Once you've got the fry, rearing halfbeak fry is pretty easy.> He is shy of my other fish but is otherwise settling in well. He even ate a little and left his safe hornwort patch to fight his reflection. <Halfbeaks generally settle in well. I hand feed mine using Needlenose forceps, offering them a bloodworm at a time. In my opinion, this helps them get used to humans as "friends" rather than potential predators. Halfbeaks are notorious jumpers and can be skittish, as you'd imagine for a fish that lives so close to the surface. They do love floating plants!> Also, I forgot to mention it before but Neal's halfbeak website address, as posted in an FAQ, does not work: http://homepage.mac.com/nmonks/aquaria/halfbeakbreeding.html <Has been moved; the link was on the bottom of the page originally sent, otherwise simply go direct, here: http://homepage.mac.com/nmonks/Projects/halfbeakbreeding.html Have stuck a redirect at that old address as well, so thanks for the warning.> Many thanks for any help with this little guy! Angela <Cheers, Neale.>

Halfbeak advice -- 03/18/08 Hello! <Ave!> About six weeks ago, I found two pairs of halfbeaks at a chain pet store. They were labeled 'Celebes Halfbeaks'. I was surprised to see them there, and asked a clerk to bag them up for me. The clerk made me promise to put them in a brackish tank. I was pretty sure that they were not brackish fish, since I recently finished reading Neale's new book, "Brackish-Water Fishes." (Great book!) <Thanks!> But, since they were in brackish water at the store, I put them into a quarantine tank with brackish water. <Ah, not ideal for most Nomorhamphus species. So far as I know, only Nomorhamphus erhardt lives in brackish water; all the others are soft/acid water beasties. That said, one store near me has a female Nomorhamphus liemi in its display brackish tank and has done so for a long time. So like a lot of "peripheral freshwater fish" (i.e., freshwater fish from marine families) they likely have significant salt tolerance.> They did fine, grew a little, and time passed and I never got around to acclimating them to fresh water. Last week, I wanted the quarantine tank, so I moved them into one of my brackish display tanks. I noticed at the time that one of the females was quite fat. Just now as I was feeding them, I noticed baby halfbeaks in the tank! They are quite large, about 1 cm or more long. I saw four or five of them, and they are very lively. <Indeed they are! And wonderfully easy to rear. The tricky bit is getting the mothers through pregnancy; once the babies are delivered, life gets a lot easier.> My question is, are these Nomorhamphus liemi? I looked through Baensch's Aquarium Atlas 1 through 3, and they look more like N. liemi than any of the other halfbeaks. <The give-away is the shape of the beak: Nomorhamphus liemi has a beak that curls, like a little beard, under the jaw.> My picture doesn't show it well, but the male's pelvic fins are yellow. I want to make sure before I do acclimate them to fresh water. If they are reproducing, they are not exactly unhappy where they are, and I want to keep them happy! <I'd leave them where they are for now. With halfbeaks, what seems to matter most of all is water chemistry stability, and if adding a little marine salt mix gives them that, I don't think they care all that much.> Thank you for your time, <You may care to peruse my "halfbeak breeding diary" at my web site, here: http://homepage.mac.com/nmonks/aquaria/halfbeakbreeding.html > Susan <Good luck! Neale.>

Re: Half-beaks I have seen half-beaks in my Local Pet shop (I use PetSmart and I have never been given bad advice.) I would like to purchase some but I would like to know more about their care and breeding. <Search at http://www.wetwebmedia.com using the Google search box and also search the web for these fish and you'll find a wealth of information.> Thanx, please respond AS SOON AS POSSIBLE! <You're welcome! Ronni>

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