Stefan van der Voort on the Bornean Leaffish, Nandus nebulosus, a member of the family Nandidae.
Scientific name: Nandus nebulosus
Common name: Bornean Leaffish
Synonyms: Bedula nebulosus, Nandus borneensis
Origin: From Thailand to Indonesia
Size: Around 12cm/4.5"
Water: In the wild; neutral pH and a fairly high GH level at around 10 with water temperatures varying between 22-25C with the potential to reach higher temperatures depending on the weather.
Aquarium: A large aquarium is certainly advised because of their size; 60cm/24" for one pair and 90cm/36" and larger for multiple pairs would be a good rule. The tank should be fully decorated with plants, wood, stones and coconut shells to provide hiding places. Do not keep them with smaller fishes for they will certainly end up as food with Nandus nebulosus being able to eat fish about two thirds their own body size. Males may be aggressive towards one another so perhaps it's best to keep one male with multiple females instead of more males, unless you have a very large aquarium.
Diet: Anything apart from dried foods. Live foods such as mosquito larvae, bloodworms, glassworms, krill, and Mysis are taken readily. Frozen foods also shouldn't be a problem. Will predate on smaller tankmates.
Breeding: I'm unaware of reports of captive spawnings. It's probable that they are cave brooders, like Nandus nandus. Eggs are deposited on the cave walls and guarded by presumably the male. When the fry leave the shell the parents may regard their own offspring as food, so it's advisable to remove either the parents or the fry. They should be able to take newly hatched Artemia and microworms right away, and one can switch to larger foods in a matter of weeks.
Notes: This relatively unknown fish is really worth keeping and breeding; many interesting observations are awaiting discovery and certainly publication, especially with the genus growing since new species are being found and described as we speak. So if one is looking for something a little more special; try this nandid.
Adult colouration: Both sexes are leaf-coloured and more or less leaf-shaped. The ground colour of the body is a very light brown with irregularly shaped vertical bars which are coloured a much darker brown. These bars also cover parts of the dorsal and anal fin, with the caudal fin being hyaline and the pelvic fins being entirely brown. From its eye run three even darker brown to almost black stripes; one is heading to the dorsal fin origin, one to the lips and the last to the throat. When scared or stressed they may show a pale to dark brown body or a light brown body with large, irregularly shaped dark brown patches. Males and females can be differentiated by the following: females have shorter fins (especially dorsal and anal fins) than males; this is probably the easiest reference.
Identification: A recent paper by Chakrabarty, Oldfield and Heok Hee Ng showed that the form of Nandus nandus at Sabah, Borneo, was a distinct species, which has been named N. prolixus. The true N. nandus should have 24-34 lateral line scales, 10-11 scales below the lateral line, 17-19 pectoral fin rays and 15-16 spines in the dorsal.
Availability: Not very often available but tends to turn up from time to time.
Price: 15 each at Wildwoods in Middlesex.
This article was first published in the Christmas 2006 issue of Practical Fishkeeping.