This weird little fish is actually a livebearer, but breeding it isn't as easy as you'd imagine, says Matt Clarke.
Common name: Pike topminnow
Scientific name: Belonesox belizanus
Origin: North and Central America. This species was introduced into Florida in the 1950s, and has formed invasive breeding populations.
Habitat: Weed-choked streams to estuaries.
Water: This euryhaline fish can live in almost any water condition from soft to hard, freshwater, brackish and marine conditions. It fares best in alkaline water with a pH of 7.5-8.0 and a temperature of around 25C/77F. Like many livebearers, these have a wide temperature tolerance, which has enabled them to live in the comparatively cooler climate of Florida.
Size: Males reach about
8-10cm/3-4", while females are bigger at 10-15cm/4-6".
Diet: Can be tricky to feed as they'll often only accept live fish such as young Guppies or platies. They can be weaned onto frozen fish, but if they do not respond, surplus livebearer fry may be the only option.
Aquarium: These are serious predators and will attack anything they think they can swallow, so keep them in a species tank or with larger fishes. A 90-120cm/36-48" tank is about right for an adult male and some females. Add plenty of bushy plants, such as Cabomba, to act as a refuge for any fry. Keep an eye on the beak as it can become infected if damaged.
Breeding: Livebearers, they produce around 100 offspring at each brood following a 30-50 days gestation period. The female can store the male's sperm in its uterus for nearly two months, allowing successive batches of eggs from one spawning. The fry are tricky to rear as they need live foods such as brineshrimp or Daphnia as a first food. Fry and young fish are cannibalistic.
Similar species: The
sub-species, B. belizanus belizanus and B. belizanus maxillosus, are no longer considered distinct.
Notes: Used in genetic research and also introduced to parts of the USA with negative consequences. Males are less common, possibly due to biased sex ratios or cannibalism in captivity.
Availability: Not seen for sale very often. These were at Maidenhead Aquatics in Harlestone Heath. No males arrived in the shipment.
Price: On sale for 5 each.
This article was first published in the September 2004 issue of Practical Fishkeeping magazine.