Have I been sold a male Fighter by mistake?
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.