How do I breed my halfbeaks?
I've had six Silver halfbeaks – not sure of the actual species – in my 120x38x38cm tank for about five months and they are now a good size. What size of tank would I need to move them to for breeding? Do they need conditioning? What is the best decor and how do I rear the youngsters? Do I need to remove the adults? JO B, EMAIL
NEALE SAYS: Breeding halfbeaks is tricky, but definitely not impossible.
Let’s start with the basics. Yes, the adults do seem to need a good diet to ensure their fertility, with at least some small live foods included. Wingless fruit flies are probably the best thing you can offer them, and these are available mail order and from pet shops catering to the needs of small reptiles and amphibians. Otherwise, a varied diet of frozen foods such as bloodworms and brine shrimp should be provided, alongside good quality flake and pellets.
So far as their aquarium goes, plenty of open space at the surface and floating plants will be welcomed. Otherwise, the decor is up to you. In my experience, halfbeaks will swim at different levels of the tank, even feeding from the bottom at times, but they do prefer to stay close to the surface. Sometimes they’ll hang about near the outflow from the filter, but at other times they’ll find areas with little water current, so it’s a good idea to provide a mix of environments within their aquarium. Juveniles in particular seem to like to lurk among floating plants in those parts of the tank with very little current. Assuming your Silver halfbeaks are a
Dermogenys species, then your present aquarium should be fine. Anything around the 100 l/22 gal mark should be fine for a small group of these little halfbeaks, and the larger species, among them the popular Celebes halfbeaks Nomorhamphus
liemi liemi, are better suited to systems upwards of 150 l/33 gal.
Sexing shouldn’t be an issue – the males are smaller than the females, often more colourful and, like guppies, have a modified anal fin used to direct packets of sperm into the females while mating. Also like guppies, the males are continually sparring with each other or trying to mate with the females. But unlike guppies, the females aren’t constantly pregnant – or, if they are, don’t seem to consistently deliver broods of healthy fry. It’s been observed that older females are less fertile than younger females, which may have something to do with their diet, but it’s hard to be sure. One problem is a tendency towards miscarriages, possibly caused by stress. While that can happen with guppies and mollies, it’s much less common, so we often leave males and females together. But when it comes to halfbeaks, you do need to separate the sexes if possible, so move the males, rather than the pregnant females. Oddly enough, halfbeaks are not especially predatory towards their fry. Given the right conditions, halfbeaks will breed without too much trouble, although brood sizes aren’t comparable to those of other livebearers. Of course, providing the right conditions can be a challenge because halfbeaks aren’t always properly identified, which makes optimising water chemistry difficult. If all else fails, neutral, moderately soft to slightly hard water is a good starting point for the bigger Nomorhamphus species, while the smaller Dermogenys prefer slightly basic, moderately hard water. Some people add a little salt (2-3g per litre) to tanks with Dermogenys, which may help if your specimens are struggling.