If you're looking for a really unusual addition to your tropical freshwater aquarium, hatchet fish might not immediately catch your attention. Although they have an unusual body shape they're rather plain in colour and they're often shy. But hatchet fish have a secret - they're the only species of fish in the world that can actually fly.
Unlike other so-called flying fish which are merely good at jumping, hatchet fish actually flap their specially shaped pectoral fins to help them move further through the air.
In the wild, this helps them to catch flying insects, and some aquarists breed fruit flies so they can feed them this way. Of course, you'll need a secure aquarium hood and a good bit of space above the water surface to keep them safe, but they're amazing to watch.
Caring for Hatchet Fish
Although they're fascinating fish to keep, hatchet fish have a reputation for being delicate, so they're not a good beginner fish. However if you provide them with the right conditions they will thrive. They are happy with quite a wide temperature range (24ºC to 30ºC) but they're sensitive about pH and need slightly acidic water. They're vulnerable to white spot, especially when stressed, so keep a close eye on them.
Hatchet fish are good community tank members, but they can be shy and are sometimes the victims of bullying. Keep them in a shoal of four to eight to make them feel more confident. They prefer to spend most of their time near the surface, so are best kept with relatively peaceful mid-water species like tetra and killifish, or with bottom-dwellers.
To reduce stress further, it's a good idea to provide your aquarium with a dark substrate and background, to give the illusion of security, and to keep some floating plants to provide hiding places near the surface.
They enjoy gentle currents that keep plants moving around. If well looked after, they will grow as long as three and half inches.
Feeding Hatchet Fish
Although watching them catch flying insects is fun, you may prefer not to keep these at home, as there's always a risk of them escaping and infesting your house.Never feed your fish wild insects as these may be contaminated with dangerous chemicals. The good news is that hatchet fish will do just as well on insect larvae, including freeze dried ones.
Because they're surface feeders, hatchet fish are often perplexed by foods like pellets and algae discs, and they'll be unable to compete with other fish for them. However almost any floating food will do, including flakes.
A bit of vegetable matter can aid their digestion but they are primarily carnivores. They enjoy eating small crustaceans and are particularly fond of mosquito larvae.
Breeding Hatchet Fish
There are several species of hatchet fish which all look quite similar and are often mis-sold; though they will all happily shoal together, they can't interbreed, so make sure you have appropriate pairs. The easiest ones to breed in captivity are marbled hatchet fish, though they are among the more delicate strains in general.
There is no difference between the colouration of male and female hatchet fish, but females, especially when gravid with eggs, are noticeably more rounded.
If you can't tell from the side, look at them from above to see this. Within a shoal, couples will pair off naturally, but they should be isolated when they're ready to breed or the eggs will be eaten quickly.
To stimulate breeding, provide a quiet, sheltered tank with soft, acidic water and plenty of floating vegetation - this is where the eggs will be laid. Remove the parents afterwards.
The fry should be fed with liquid food for the first few days, but will soon be able to move on to a diet of rotifers and crumbled flakes.
Although they require a bit of extra care, hatchet fish are fascinating pets and can make a great addition to your aquarium.