One of the fun things about the aquarium hobby is that there is always something new to work with. Anyone who says they have become bored with the hobby hasn’t really looked around. There is an entire group of fish from many families affectionately and collectively known in the hobby as “oddballs.” One of the few common characteristics of this diverse group is that there is little information out there about them. When information is found, it is usually secondhand, and if you check several sources, especially online, it is easy to see that the exact same information is being regurgitated over and over. So consider this column a special one, as it includes firsthand information about one of these oddballs.
Xenentodon cancila is a member of the group of fish known as needlefish. Needlefish are long, slender and have narrow jaws full of sharp teeth, indicating that they are predators. The vast majority of needlefish are marine; a few species are commonly found in brackish water, and one or two species — including our subject this month — are found in freshwater streams and rivers near the coast.
The freshwater needlefish is neither for the casual aquarist, nor the community tank. It is a predator that is usually sold as a 5- to 6-inch juvenile. According to the literature, this fish can grow to 16 inches, but I’ve never seen one in the hobby larger than 10 inches. It is still a big fish needing at least a 4-foot-by-18-inch tank and preferably a 6-foot or larger tank. Surface area is key. A wide, long, shallow tank is preferable to a deep tank with the same gallonage. This is a schooling fish that should be kept in groups of at least six, especially if you want to breed them. A group of eight is perfect for a 75-gallon tank.
The freshwater needlefish is found over a wide area of coastal Southeast Asia, so this species is not picky about water parameters. Hard, alkaline water at 75 to 80 degrees Fahrenheit is perfect. A substrate designed for African Rift Lake fish will help maintain water parameters. Add a liquid trace mineral supplement after each water change just to make sure the water stays stable. Salt is unnecessary. Plant the tank with clumps of Java fern and Java moss arranged around the perimeter with a large open area for swimming. A species tank works best. Large regular water changes will keep the water in pristine condition (50 percent twice a week, as this fish can be messy). Any commercial filter will be acceptable.
In the wild, the freshwater needlefish is an ambush predator, hanging around just under the water’s surface and waiting for insects to land on the water. Its needle-sharp teeth are designed for grabbing and holding prey, just like those of a crocodile.
The freshwater needlefish also eats small fish and crustaceans. In captivity, it is often fed a diet of small feeder goldfish. Goldfish are not a good food for any fish. Instead, give this species a varied diet of ghost or cherry shrimp, medium-sized redworms and feeder guppies. It also takes frozen krill, Mysis shrimp, freeze-dried and live crickets, and houseflies. A freshwater needlefish will grow quickly on this diet and will soon be ready for spawning.
My male needlefish have dorsal fins edged in black, and their anal fins have a concave edge. Some sources report that this fish also has a black line on the anal fin, but my fish don’t have that. My males are a bit smaller than the females (7 inches versus 9 inches). The males display for one another and court the females every day.
Spawning is a fairly simple affair. The males dance in the open for the females, and if a female shows interest, the male courts her with a convulsing dance while swimming alongside her. If she allows it, the male wraps her anal fin with his. The pair then moves into the Java moss and Java fern around the perimeter of the tank. Each time they do this, a huge single egg is released (larger than one-eighth inch in diameter). Once they begin spawning, each pair will lay up to a dozen or so eggs over the course of an hour or two. They will spawn daily for a couple of weeks, and a pair can easily lay more than 100 eggs in this time period.
The parents ignore the eggs, but it is still a good idea to remove the eggs. They are fairly tough, so you can pick each egg from the plants by hand, just as with killie or rainbowfish eggs. I move them to a shallow pan filled with water from the adults’ tank, and I change the water in this pan every day. Hatching takes about 10 days, and it is interesting to watch the development of the larvae in the large egg. By about day four you can see the heart beating with a magnifying glass and watch the young fish as it moves around in the egg. When they hatch, they are huge — nearly half an inch long — and ready for food. They will take newly hatched brine shrimp and small Grindal worms right away, and within a few days, they will take the larvae of confused flour beetles (yes, they are actually named “confused” flour beetles) and adult fruit flies. Some breeders also feed them young fish (baby gouramis and guppies are recommended), but I have not found this necessary. As the fry grow, keep them segregated by size, as larger siblings will eat smaller ones (even those that are three-quarters their own size).
Within two months, the fry will be large enough for you to find homes for them. If you have built up a good rapport with the owner of a local fish store, you will likely be able to trade them for food and other supplies. If you reach this point, congratulations! You’ve completed another successful adventure in fish breeding. AFI
Mike Hellweg is active in local and national hobby organizations and has had many articles published in various publications. He currently owns and operates a retail fish business.