Nathan Hill tracks down the big boys of the tiny catfish crowd and gives them the limelight he thinks they deserve.
The hobby has embraced the Corydoras family with open fins and it’s hard to find a tank without a clutch of these diminutive, benthic and charismatic fish.
Less popular, however, have been their bigger brothers, the Brochis cats. Brochis only comprise three species — B. splendens, B. britskii and B. multiradiatus — and of these only splendens is seen with any real frequency.
Some taxonomists would deny that Brochis actually deserve their stand-apart naming.
There’s certainly firm evidence of close genetic links with Corydoras species among the three, with many eyes focused on examples like C. sodalis and C. geoffroy alongside some others.
However, for the moment, Brochis look set to stay — despite some retailers continuing to choose to mark B. splendens up as Emerald corydoras.
What marks Brochis out from their cory ilk are both their size and the arrangement of their fins.
They tower over smaller corys, having deeper and considerably more thick-set bodies, but if you’re still in doubt about identification then look closely at the dorsal fins.
Corydoras will have eight to ten rays in their dorsal fins, while Brochis have far more than this paltry total.
B. splendens has the least of the three species, with ten to 12 dorsal rays, and both B. multiradiatus and B. britskii have 15 to 18.
Distinguishing between B. britskii (above) and B. multiradiatus (pictured at the top of the page) is a case of scrutinising the snouts. B. britskii has the bluntest nose of all and B. multiradiatus has a long, sloped and slightly saddled snout — which is all the better for grubbing about in the substrate.
B. britskii supposedly has the largest eyes of the trio, but this can be quite hard to ascertain and shouldn’t be relied on as the primary indicator.
All that gas
All Callichthyd catfish are known to ingest atmospheric air and Brochis have been well studied for their gulping activities, even in water with full oxygen saturation.
The main function of air swallowing is ventilation. These cats have a highly vascularised gastrointestinal system, capable of extracting oxygen directly from the ‘trapped wind’ and passing it into the blood. Unlike true breathing, carbon dioxide does not leach back into the gas bubble and as the fish absorbs its pocket of air its buoyancy changes.
So much air is taken in per gulp that the fish has a variation of some 13% in buoyancy between gulps, starting off with more floatation and gradually losing it as it ‘belly breathes’.
These gasps of air are not obligatory, as is found with some fish species, but merely facultative. If unable to reach the water surface then the Brochis will increase respiration through the gills, but show no other signs of asphyxiation or suffering.
Unlike some Callichthyd catfish that like to take their gulps with synchronicity – such as Hoplosternum that breathe air as a collective – Brochis are bold enough to venture alone to the surface, often using the journey to expel any remaining gas in the abdomen as a discrete bubble along the way.
No place like home
Brochis catfish are bigger than people expect, but well within manageable realms. From reported adult sizes as far adrift as 6.7-11.5cm/2-6-4.5”, in most aquaria they will peak somewhere around the 8-9cm/3-3.5” mark. At this size they become dashing inhabitants of the tank, with some striking metallic green colours on full show.
In their natural habitat, they inhabit small streams to larger rivers, generally keeping themselves close to banks where flow is more restricted.
Vegetation is hidden among where it’s found and leaf litter is pounced on in puppy-like fashion, with the fish eager to dip their snouts for treats underneath.
South American cats, they are found in Brazil, Colombia, Peru, Ecuador and Paraguay, pending species. B. splendens is distributed across most of these countries, although others, especially B. britskii, is more isolated.
Feeding is easy, but often performed incorrectly. Wild morsels include aquatic insects, crustaceans and worms, but in aquaria these fish are often offered a dry and uninteresting diet.
Admittedly, it’s quite humorous watching Brochis chasing a sinking wafer around the tank, one end to the other, but these fish will do well to receive lots of live and frozen foods.
Like other catfish, these are not cleaners surviving or thriving on the scraps of others and will soon weaken and become hollow bellied if missing out on their own food.
Substrate needs to be considered prior to purchase, with all species preferring finer grades of sand to gravels. Coarse gravels are to be avoided entirely, damaging the bristles of the fish. A whisker-free catfish is the sorriest of sights.
Maintain fine substrates well, as anaerobic patches can develop, especially if used in tandem with leaf litter. Almond leaves can make them comfortable and encourage more activity.
Without periodic sifting and raking, the base of the tank can start to harbour high levels of usually non-pathogenic bacteria, all waiting to exploit the first cut appearing on a fish.
Décor is preferred when consisting of root tangles and dense planting. Broad leafed, floating, bushy or stem plants – Brochis are more comfortable when growth is abundant, even during the bright lights of the daytime.
Unfortunately, because of their size, they tend to be housed in tanks where Corydoras would be considered too delicate to stand up to other residents. Often the fish will be seen alongside bolshie, medium-sized cichlids — but this is far from ideal.
Smaller cichlids like Apistogramma tend to be unnerved by large, roaming Brochis and bigger cichlids can give them a hard time, so it might be worth adding them as a complement to larger tetras — or why not consider a broader and shallower ‘riverbank’ biotope, with Brochis as the focal point?
Adequate numbers should be kept and the trade myth that ‘three or so’ will be happy together needs to be addressed. Greater numbers equate to greater confidence and never aggression. A few dozen would make amazing viewing, but don’t be tempted to drop below six of any one species.
Be cautious when purchasing Brochis of any species. If imported wild from South America, as many are, there’s a high incidence of fish carrying Piscinoodinium, or freshwater velvet disease.
This can be hard to spot, given the metallic sheen of the fish, but surefire signs are scratching and belly scraping, along with cloudiness of the skin and eyes. Fish that carry it are often already stressed from transit, starved prior to being shipped and have little chance of recovery.
Never be tempted to buy a scratching specimen in the hope of reviving it. Piscinoodinium can spread far more rapidly than whitespot and such an exercise is almost certain to fail.
So can you find a place for a big dwarf that nobody wants? With ever more exciting Corydoras imported yearly, it’s hard to imagine this bigger, blander offering having much mileage.
However, given a chance and kept correctly, I’ll wager that you’ll soon fall for these gentle giants and agree that they deserve more than being relegated to dealers’ ‘also ran’ tanks, eventually being discounted to clear.
Some cowards have spines
Handle Brochis with care. Although not venomous, and having a bite that’s roughly as dangerous as a snail’s, they do have one last-ditch trick in their spiny fins.
The two pectoral fins, along with the dorsal fin of these cats, can be locked out in a triangulated position, turning these little fellows into a spear-tipped swallowing obstacle that lodges in the throats of predators.
In the wild they have few natural enemies, aside those with strong enough mouths to crush the protrusions.
These cats panic with hair trigger speed and netting them out of the tank will see them instantly assume the posture of fins out and ready.
If grabbed, or held with too much force, these spines will easily penetrate hands, even through thick rubber gloves and the ensuing infection from those grubby spines is not something that any hobbyist will want to experience with any frequency.
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