How do I keep these oddball characins?
I want to set up a tank for Striped pike characins and I’d like some advice on how best to do that, please. I want them to feel as settled as possible because I don’t what them to damage their jaws if they get spooked, so advice on décor would be useful. Is there any information you can offer on feeding — can they be converted onto dead food?
What size of tank is best and is there anything I can keep with them safely — or should I just stick with the characins? I’ve been keeping fish for six years, but this is the first time I’ve set up a specialist tank like this.
JAMES SIMPSON, VIA EMAIL
NEALE RESPONDS: Boulengerella lateristriga comes from South America, and is a lovely fish, but it’s rather more difficult to keep than the robust Rocket gar, Ctenolucius hujeta. Indeed, if this tank is going to be your first go at predatory characins, there’s a lot to be said for choosing C. hujeta as your starting point instead. They’re smaller, less nervous, less fussy about water chemistry, and generally more accommodating in terms of food. They will learn to take all sorts of foods, including good quality floating pellets, such as Hikari Cichlid Gold, and even things like frozen bloodworms and strips of seafood are readily accepted. I fed mine by offering bits of prawn or fish, using needle nose forceps.
By contrast, Boulengerella are much less happy in the confined space of an aquarium. This may be because their natural habitat, the dark and thickly vegetated margins of large lakes, is one that allows them to blend into the background, safe from the larger predators while remaining hidden from their prey. Ctenolucius seem to be happier in open water and less bothered by overhead light, and their ability to use air as a source of oxygen indicates a preference for habitats most other fish cannot occupy. Being naturally removed from some of their potential competitors or predators,
Ctenolucius don’t need to be quite so flighty, and on the whole, they’re pretty chilled out fish that do well in captivity.
Boulengerella are very different and will jump at anything even vaguely threatening. Furthermore, lacking the air-breathing adaptations of
Ctenolucius, they appear to be much more sensitive to low oxygen levels and ‘old’ water. So, the aquarium designed for these fish needs to be very carefully constructed and maintained. Water depth isn’t critical, but surface area is. Both Boulengerella and Ctenolucius seem to get along well in single-species groups, and aiming to keep at least three specimens is a good idea. I’d be looking at something like 60cm front to back, and maybe 180cm in length at a minimum. With Boulengerella, feeling ‘boxed in’ is what’s going to make them more prone to jumping or crashing into the sides of the tank.
You need to avoid tankmates likely to spook them. Even L-number catfish could stress them, especially at night. Instead, I’d be looking at things like the larger whiptails such as Sturisoma that move about so little or so slowly that the Boulengerella will quickly learn to accept them. Still, the ideal would unquestionably be to keep them alone.
So far as decorating goes, Boulengerella appreciate overhead shade. I’d suggest a mix of bogwood roots to create vertical structures around the edges of the tank that would keep it away from the glass. Tall plants might be used, especially things with floating leaves, such as Vallisneria, but the easiest option would likely be some sort of floating plant species such as
Amazon frogbit for greenery. Keep the lower levels uncluttered, so that the fish can swim easily in and out of shady areas as it wants. Smooth silica sand would be the idea substrate, but gravel would work too. Oddly enough, water chemistry isn’t crucial despite their natural blackwater habitat. Just avoid water that’s too hard; anything between 1-12˚dH should be fine. Space, oxygen, water quality, and a decent diet all seem to matter rather more to long-term success.