Have I been sold a male Fighter by mis­take?

Practical Fishkeeping (UK) - - Advice -

My 30 l/6.5 gal tank con­tains two fe­male Si­amese fight­ers, bought to­gether from the same sup­plier from the same dis­play tank. They usu­ally get along fine, but re­cently one has dou­bled in size com­pared to the other, and has been con­stantly chas­ing the smaller one.

We no­ticed that the smaller of the two be­gan to de­velop a fat­ter belly and to­day has started to drop what we pre­sume are eggs. We have sep­a­rated her for now. Is the larger Fighter a male then, and are the eggs likely to hatch? DAVID JESSOP, EMAIL

NEALE SAYS: It is very un­likely that you were mis­tak­enly sold a male Fighter in­stead of a fe­male. Male and fe­male Fight­ers are kept en­tirely sep­a­rate not long af­ter they hatch, and the mass-pro­duced longfin va­ri­eties you see in most shops are al­most cer­tainly go­ing to be cor­rectly iden­ti­fied as males and fe­males any­way, sim­ply be­cause of the way they’re farmed and the strik­ing dif­fer­ences in fin length and coloura­tion.

That said, the short­fin va­ri­eties of Betta splen­dens might be mis­taken un­der some cir­cum­stances, es­pe­cially now se­lec­tive breed­ing has pro­duced fe­males with bright colours and longer fins. Here, be­hav­iour is of­ten taken as the best in­di­ca­tor, males tend­ing to be much more ag­gres­sive to­wards ri­val males and non-re­cep­tive fe­males.

Fe­males also have more rounded ab­domens and of­ten a clearly vis­i­ble off-white gen­i­tal papilla just in front of the anal fin. The equiv­a­lent struc­ture on the males is rarely vis­i­ble out­side of spawn­ing.

In terms of coloura­tion, the fe­males of­ten have paler bod­ies, even if their fins have plenty of colour, and two or three dark, lon­gi­tu­di­nal bands are fre­quently vis­i­ble on the flanks. Male and fe­male Betta splen­dens are oth­er­wise sim­i­lar in terms of shape and size, but males usu­ally have longer ven­tral fins and more ob­vi­ous ‘frills’ to their gill cov­ers, used when mak­ing threat dis­plays.

The fact is that fe­male Si­amese fight­ing fish will of­ten squab­ble. The dif­fer­ences in ag­gres­sion be­tween male and fe­male fish is more of­ten a dif­fer­ence of de­gree, rather than an ab­so­lute ‘one is, one isn’t’ sort of thing. So where males are ag­gres­sive, the fe­males can be too – just not so much. You see this in many ci­ch­lids, half­beaks and live­bear­ers, where the males may well do a lot of the fight­ing, but the fe­males are by no means com­pletely pas­sive, even to­wards one an­other.

Some aquar­ists keep what they call soror­i­ties – aquaria stocked with sev­eral fe­male Betta splen­dens. Th­ese work best when there’s a fair num­ber kept to­gether, so per­haps half a dozen or so in a 75 l tank would be a bet­ter bet than two or three in a tank half that size. The tank needs lots of sur­face area be­cause Betta are air-breath­ing fish that cre­ate their ter­ri­to­ries in float­ing veg­e­ta­tion.

That said, th­ese soror­ity tanks are of­ten a bit hit-and-miss in terms of suc­cess. Per­son­ally, I wouldn’t try one with­out hav­ing a ‘plan B’ in case things went wrong. It’s much eas­ier to keep a sin­gle Betta fe­male along­side dis­sim­i­lar tank mates, for ex­am­ple Co­ry­do­ras cat­fish.

Betta eggs are laid in a float­ing bub­blen­est built and main­tained by the male. With­out the male guard­ing the eggs and en­sur­ing the fry have easy ac­cess to air, there is vir­tu­ally no chance of them sur­viv­ing. It should be ob­vi­ous if the male is build­ing a nest, and if there’s no ev­i­dence of that, you can prob­a­bly as­sume both fish are fe­male.

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