I would like some advice on setting up a biotope style aquarium for black ghost knifefish. I have a 450-litre tank which is currently empty, and I wondered if you could give me some advice on whether such a biotope would work?
ALEX LEWIS
TROPICAL
NEALE ADVISES: The black ghost knifefish, Apteronotus albifrons, naturally inhabits rivers and streams, particularly in areas with strong currents and lots of oxygen. Its long, slender shape is an adaptation that allows it to explore crevices, whether for finding food or avoiding predators, so a rocky tank would seem a good starting point when it comes to decoration. But while a tank decorated with tall slates and boulders is a good start, there might be some nuance to this. Under lab conditions, a closely related but smaller species, Apteronotus leptorhynchus, was found to spend the daytime hiding among plants or tall rocks. During the night, however, it showed no particular preferences for any of the habitats offered, and would move freely between planted areas, rocky areas, and open areas of sand or gravel.
Similarly, ecologists studying the distribution of another species, Apteronotus rostratus, found them mostly among the leaf litter trapped between rocks and sticks, and very rarely in the deeper parts of rivers with slow water currents and no leaf litter.
While we can’t be sure the less well-studied black ghost knifefish follows the pattern set by its relatives, there’s probably some overlap, and we should be thinking more in terms of a complex mix of habitats than just one single type of decoration. A tank with some rocky hiding places, a few tall stands of plants, and some open patches of sand or gravel could all be included in the tank. Once settled in, these fish have proven to be extremely curious and outgoing, so offering a complex environment will probably suit them well.
The common thread to all the observations made of black ghosts in the wild is that they come from places with strong water currents, so it’s likely that turnover and oxygenation, rather than decor, are the things to get right. I’d be aiming for a turnover rate of at least eight times the volume of the tank per hour, and ideally a bit more. This could come entirely from the filter, or from a combination of filters and powerheads dotted about the tank.
On the whole, once these fish are settled in, they have proven to be quite adaptable and even hardy. Water chemistry isn’t terribly important, though slightly soft and acidic
