They’re odd look­ing, frag­ile and like to wres­tle each other. But Ga­bor Hor­vath says they’re well worth the ef­fort.

Practical Fishkeeping (UK) - - Contents -

Dis­tinctly odd-look­ing, slen­der Wrestling halfbeaks are highly rec­om­mended if you want to keep (and breed) some­thing just a lit­tle bit dif­fer­ent.

There are beau­ti­ful fish and even more beau­ti­ful fish. There’s no such a thing as an ugly fish – I pre­fer to call them odd.

The half­beak fam­ily, hemi­ram­phi­dae, got more than its fair share of odd­ity, with over­grown lower jaws and rugged heads – just take a closer look at them. Most of the halfbeaks are ma­rine species, but there are a few in­ter­est­ing live­bearer ones that spend their lives in fresh­wa­ter or brack­ish-wa­ter en­vi­ron­ments.

The halfbeaks avail­able in the mar­ket share many sim­i­lar­i­ties, but there are still some sig­nif­i­cant dif­fer­ences be­tween them that you need to con­sider if you want to keep and breed them suc­cess­fully.

The fresh­wa­ter halfbeaks most fre­quently sold in the UK be­long to the gen­era Der­mogenys and

No­morham­phus, and here we’ll be look­ing at the for­mer of those.

These slen­der pike-like fish had been on my aquar­ist bucket list for ages, but for some rea­son I couldn’t get hold of any. Then my luck changed and I spot­ted a nice group of Wrestling halfbeaks at the JMC aquat­ics’ stand at the aqua Telford show. For­tu­nately they let me have 10 of them (thank you, Jane!) and I could be­gin my half­beak project.

I’ve learned a lot about these in­ter­est­ing and very love­able fish in the past few months, so now it’s time to share this knowl­edge.

The trio

The genus Der­mogenys in­cludes sev­eral species, such as D. pusilla,

D. suma­trana and D. sia­men­sis. The small­est and the least colour­ful of the trio is Der­mogenys sia­men­sis, barely reach­ing 4cm in length. In the other two species, the fe­males can grow up to 7cm while the males stay a lit­tle smaller, peak­ing at 5cm.

Colour-wise, the two larger species are quite sim­i­lar, with the

males sport­ing orange or red­dish dor­sal and anal fins. The eas­i­est way to tell them apart is based on the po­si­tion of the ven­tral fins. In the case of the true Wrestling half­beak,

Der­mogenys pusilla, they’re po­si­tioned around mid­way be­tween the pelvic and the anal fin, while

Der­mogenys suma­trana has them closer to the anal fin.

Wrestling halfbeaks can vary greatly in body colour, from the ‘nat­u­ral’ sil­very brown, through to gold, and to the al­most white ‘plat­inum’ va­ri­ety. All three

Der­mogenys species men­tioned make ap­pear­ances from time to time in the shops, and all are traded un­der the col­lec­tive name of Wrestling half­beak.

Nat­u­ral fight­ers

The ‘wrestling’ moniker orig­i­nates from the males’ keen­ness to get in­volved in ter­ri­to­rial dis­putes with their ri­vals – a be­hav­iour that’s es­pe­cially prom­i­nent in wild-caught fish. Those long beaks serve a pur­pose – to de­cide who’s boss they grab each other’s beak and try to wres­tle down their op­po­nents. These fights can some­times last over an hour, es­pe­cially in the con­fined spa­ces of aquaria.

In the fishes’ coun­tries of ori­gin, peo­ple use them for fish-fights, with bets placed on the out­comes, just as hap­pens else­where with Si­amese fight­ing fish. In aquaria this fight­ing spirit is un­wanted, but with clever po­si­tion­ing of tank

Halfbeaks are very in­ter­est­ing and chal­leng­ing fish to keep and breed. I can strongly rec­om­mend them to those want­ing some­thing dif­fer­ent

decor we can sig­nif­i­cantly re­duce fight fre­quency by break­ing up lines of sight and di­vid­ing the tank into dis­tinct ter­ri­to­ries.

My fish are for­tu­nately quite docile, as they were prob­a­bly tank-bred, so most of the time their sparring only goes as far as a bit of fin-flar­ing and mouth-gap­ing. Some­times the fe­males also join in the ter­ri­to­rial dis­putes, but those don’t last for long. The plen­ti­ful float­ing plants (Salvinia) in my tank def­i­nitely help to re­duce ag­gres­sion, as they break up the lines of sight and also of­fer a re­treat for the weaker fish.

Mak­ing a home

The nat­u­ral habi­tats of the

Der­mogenys halfbeaks in­clude slow-mov­ing rivers and still wa­ters in South-east Asia. Most of these biotopes have dense veg­e­ta­tion, with float­ing plants or sub­merged plants reach­ing up to the sur­face. Halfbeaks spend most of their time among this sur­face green­ery, wait­ing for an oc­ca­sional in­sect to fall in. Their elon­gated lower jaw and up-fac­ing mouth en­ables them to quickly pluck the un­for­tu­nate fly from the sur­face. To keep them in peak con­di­tion we should pro­vide them with a sim­i­lar en­vi­ron­ment and diet in the fish tank. As Halfbeaks, es­pe­cially those be­long­ing to the Der­mogenys genus, tend to stay near the top, the amount of sur­face area is much more im­por­tant than the height of the aquar­ium. A fish tank with a 90x45cm base and a tight-fit­ting cover is per­fect to house a small group of them. They’re very adapt­able and can be kept in a range of wa­ter con­di­tions, so long as the ex­tremes are avoided and the wa­ter qual­ity is pris­tine. Fill up their tank with wa­ter around 23-26°C, with a hard­ness of 5-15° and keep it close to neu­tral – 6.5-7.5ph – and you should have no prob­lems. Keep the pa­ram­e­ters steady, as these fish can be sen­si­tive

to sud­den changes in both acid­ity and tem­per­a­ture.

Some­times, halfbeaks can be found in brack­ish habi­tats in the wild, and to mimic this some aquar­ists put a lit­tle aquar­ium salt into their wa­ter. It’s not es­sen­tial though, and ev­ery species dis­cussed here will hap­pily live and breed in com­pletely fresh­wa­ter tanks at the pa­ram­e­ters listed above as well.

Dec­o­ra­tion-wise, they’re not very fussy. Ba­si­cally, they don’t care about any­thing be­low their eye level. When choos­ing decor avoid hard rocks and other sim­i­lar blunt ob­jects, which could dam­age their beaks.

Beak in­juries are quite fre­quent, as halfbeaks are eas­ily spooked. When star­tled, they dart around the tank like tiny mis­siles, hit­ting the glass or jump­ing out of the wa­ter al­to­gether. So for the first few days af­ter their ar­rival, be very care­ful when ap­proach­ing their tank.

Use lots of float­ing plants or other veg­e­ta­tion reach­ing the sur­face to help re­lieve this ini­tial stress. Dense float­ing veg­e­ta­tion also helps if you want to breed them, as it pro­vides pro­tec­tion for the new­born fry.

Per­se­vere and in time your fish will learn that your ap­pear­ance means food and they’ll be­come braver. My Wrestling halfbeaks are al­ways the first to get to the food now, fre­quently pok­ing my fin­gers with their beaks to re­lease their favourite treat of blood­worm.

Feed­ing and tank­mates

Halfbeaks are not very picky eaters, as in na­ture they would grab any­thing edi­ble fall­ing into the wa­ter, be that a worm, in­sect or plant. If you im­i­tate this nat­u­ral va­ri­ety by feed­ing a range of frozen meals – blood­worm, Artemia or DIY frozen food – as well as flakes, float­ing gran­ules and live foods such as Daph­nia, mos­quito lar­vae and fruit­fly, they will be eter­nally grate­ful. The only thing to re­mem­ber is that if the food sinks fur­ther than 15cm or so from the sur­face, the halfbeaks will rarely bother to fol­low it. To avoid wa­ter pol­lu­tion, it’s a good idea to keep some clean­ing crew with them to pick up these fall­ing morsels. De­spite the pike-like, preda­tory ap­pear­ance of halfbeaks they’re gen­er­ally peace­ful and can be kept well to­gether with sim­i­larly sized com­mu­nity fish. Avoid bois­ter­ous fish as tank­mates, as halfbeaks won’t with­stand even light har­rass­ment. Also avoid ex­ces­sively small fish (like Bo­raras mi­cro­ras­b­ora), be­cause they may be con­sid­ered as din­ner.

I house my halfbeaks with Pea­cock go­b­ies, Ta­teurn­d­ina ocel­li­cauda, and it’s a match made in heaven – the halfbeaks al­ways stay near to the sur­face, while the go­b­ies oc­cupy the lower re­gions, breed­ing away.

Co­ry­do­ras cat­fish, mol­lies, platies, small rain­bow­fish and deep-bod­ied tetras are all suit­able tank­mates.

Baby ‘beaks

Der­mogenys halfbeaks are live­bear­ers, but prob­a­bly the hard­est of the halfbeaks to breed. Even when suc­cess­fully bred, the brood is quite small, con­sist­ing of only six to 20 young­sters af­ter a 26-42 day ges­ta­tion pe­riod, de­pen­dent on tem­per­a­ture.

The dif­fi­culty isn’t get­ting them preg­nant, as ma­ture males make con­stant use of their an­dropodium – a mod­i­fied fin-ray used as a re­pro­duc­tive or­gan, much like those of gup­pies – to en­sure prog­eny.

The prob­lem is that fe­males will give birth pre­ma­turely if fright­ened, or pro­duce still­born fry de­spite

be­ing given the best pos­si­ble care.

One rea­son of­ten given for this is the lack of cer­tain vi­ta­mins in the adults’ diet. I’ve al­ways tried my best to pro­vide my fish with rich food, which in­cluded reg­u­lar por­tions of black mos­quito lar­vae from my wa­ter butt. Nev­er­the­less, I was still a bit ner­vous when I saw two of my fe­males get­ting pro­gres­sively plumper, which is a sure sign of an on­go­ing preg­nancy.

I’d read con­trast­ing re­ports about adults prey­ing on their fry, so to en­sure the sur­vival of the off­spring, I moved one of the fe­males to a well-planted sep­a­ra­tion tank when I thought the time was right, and di­vided my breed­ing aquar­ium into two with a hard plas­tic mesh to pro­tect the new­borns.

I must have guessed the tim­ing right, as next morn­ing I found eight tiny sil­ver ‘splin­ters’ hid­ing among the veg­e­ta­tion. Com­pared to the fry of com­mon live­bearer types like platies, these were quite large at around 6-8mm long. This meant feed­ing them caused no prob­lem at all, as they ac­cepted newly hatched

Artemia and pow­dered float­ing flakes straight away.

In­ter­est­ingly the new­born fry of the halfbeaks have no beaks yet – they just look like a ‘nor­mal’ fish. It takes a few weeks be­fore they be­gin to fully re­sem­ble their par­ents.

Since my first suc­cess I’ve had sev­eral broods, the largest con­sist­ing of 14 fry. Luck­ily I didn’t ex­pe­ri­ence any of the preg­nancy is­sues, prob­a­bly due to the ex­tra care taken around wa­ter changes and a var­ied diet.

The lat­ter is a key fac­tor to suc­cess. I did a small ex­per­i­ment to see the ef­fect of feed­ing on the de­vel­op­ment of the ju­ve­niles. I di­vided one lot of fry into two, feed­ing the first group with high-qual­ity dry food only, and the sec­ond with a va­ri­ety of live and frozen fare. Among the mem­bers of the first group, half of the fish be­came some­how de­formed and even the rest re­mained much smaller than the ‘lucky’ fry in the sec­ond group. They ob­vi­ously wouldn’t make ideal breed­ing stock.

Wrestling halfbeaks are in­ter­est­ing and chal­leng­ing fish to keep and breed. I can strongly rec­om­mend them to those want­ing some­thing a lit­tle dif­fer­ent. If you’re pre­pared to go the ex­tra mile and treat them well, I’m sure these happy halfbeaks will give you a smile.

The ‘nat­u­ral’ sil­very brown male (be­low) and fe­male (above).

Blood­worm is a favourite food.

BE­LOW: You can see where the beak will de­velop from in the fry.

ABOVE: Fry look supris­ingly nor­mal, not even quar­ter­beak.

BE­LOW: Less strik­ing, but the nat­u­ral strain is more colour­ful.

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