Bristly subjects for the aquarium


Bristlenoses are the prettiest of the uglies, says Nathan Hill. And who can resist those puckered lips, clinging to the glass, combined with their penchant for guzzling up algae?

Bristlenose catfish are numerous and here to stay. They are an aquatic success story, acting as a surrogate replacement for the larger, more common 'plec' catfish traditionally sold to clean aquaria, only to outgrow their home and sit there, glum and unable to move.

Many Pterygoplichthys owe their freedom from restrictive tanks to their bearded, miniature kin.

There are currently 64 species of bristlenosed Ancistrus catfish listed on FishBase. Some sources cite even higher numbers, and often synonyms are slipped into the mix, resulting in lengthy forum rows.

Even the identity of the 'common' Ancistrus is open to debate, depending on how obtuse you choose to be.

The history of the original bristle is sketchy at best, though it’s now widely recognised that Ancistrus cf. cirrhosus was the trade’s first, imported into hobbyist aquaria back in the roaring 1920s.

Old salts might claim that A. dolichopterus or A. temmincki are 'truer' originals, but weight of opinion is stacked against them.

Ancistrus are not a one-size-fits-all catfish, though they carry many similarities. They all remain small, usually 8-15 cm/3-6” fully grown. All are bottom dwellers and all carry unique facial adornments.

They occur across a wide expanse, not just geographically but also biotopically. There are fast water Ancistrus, near stagnant pool inhabitants, white water, clear water and black water constituents — and this is important when planning a Bristlenose biotope. Get parameters for the wrong fish and you’ll have an unhappy inhabitant, especially with wild-caughts.

Ancistrus with paler grey and brown colours, and with elaborate patterns, tend to inhabit clear or white waters with turbulent flows, whereas species much darker and/or speckled with light dots tend to originate from slower blackwaters.

There are even fascinating – if unseen in the trade – troglodont Ancistrus species. These cave dwellers inhabit regions of little life, living a photophobic existence secreted from even a hint of light.

Even with their regressed, degraded eyes, their requirements are high and it’s not even fully ascertained what they feed on.

This natural glut of habitats and conditions means that there’s a Bristlenose for nearly all South American community tanks and communities in general.

Research before purchase, though, and don’t assume that just because a species is kept in slow water in your store that it will be happy this way for ever. Many stores are often blissfully ignorant of the exacting requirements of the Bristlenoses in their care.

There are theories as to why Ancistrus have those bristles, but what’s certain is that sexual inequality is involved, with only males sporting facial tufts. Females may just have the tiniest stubble, especially on the fringes of the lips.

Female Ancistrus like their men to be responsible and will generally opt to breed with one that already has eggs or young in tow. However, that makes non-starters of those who have not yet founded a family.

So the theory goes that the bristles, pronounced and wriggling on the face, mimic the effect of a male guarding fry. The female glances at the beard, considers the male to be fecund and viable, and opts to reproduce with him.

In fact, the males are sometimes so attractive to females that they will be caring for multiple spawns, all at different ages and all by different partners!

Losers evicted

Males can be incredibly guarded over their offspring, so take care when housing multiples together. A fight over territory can result in the ousting of the submissive fish from its cave. The victor will then swim inside and consume the other’s eggs or fry there.

The idea that these fish could even stomach eggs and meat might shock, but Ancistrus are omnivorous. You may think they’re uniquely algae feeders, given those superbly adapted mouthparts and constant rasping behaviour, but flesh is important and this is where some get their care very wrong.

Though omnivores, their requirements aren’t split 50% meat, 50% vegetable. Rather, the majority of species are closer to 90-95% vegetable matter, with 5-10% ‘meatier’ foods. However, some species have a much higher flesh requirement.

Some of what they eat is aufwuchs, which translates as a collection of tiny organisms that live within the surface film of algae growth. Aufwuchs can be made up of things like tardigrades and insect larvae and Ancistrus enjoy the occasional aquatic crustacean too.

Offerings of Daphnia, Cyclops and similar are readily taken, although don’t overfeed with these. Bloodworm is easy to overfeed, resulting in bloated fish. If this occurs revert to greener foods.

Vegetable matter needs to make up a large part of their subsistence and all too often it’s thought that algae alone will sustain. It rarely, if ever, does, especially in the confines of a tank.

Offer such as courgette slices, spinach — which can be broken down by slightly steaming until soft — dandelion leaves, potato and similar, frequently, if not daily, to graze on. Fresh greens can be weighted, using plant weights or even a metal spoon on which offerings can be skewered.

Food obsession
Left to their own devices these fish become obsessed with dried foods left by other fish, though don’t think of them as just 'cleaning up'. They simply like to supplement what can be a naturally sparse diet with high protein morsels — whenever they appear.

In a similar way to humans who cannot turn off their tastes for fats and sugars, these have learned to exploit rich meals when they present themselves and can easily become gorged.

Even be vigilant with some of the branded catfish foods that appear to use a disproportionate amount of higher protein meal, such as white fish flesh.

Some Ancistrus can ingest atmospheric air and utilise it through their highly vascularised stomachs. In extreme cases, they can supplement their oxygen intake by swallowing air.

The lay aquarist needs to be mindful of this behaviour as Bristlenoses will not do this when conditions are normoxic — having adequate levels of oxygen dissolved into the water. Although they can turn to air as a last resort, to display this behaviour screams of a deeper-seated problem needing to be addressed.

As for health, Bristlenoses are generally robust, though still susceptible to the usual problems that can affect any captive aquarium fish.

Be particularly vigilant in looking for signs of emaciation or hollow belly, especially on new imports. Often the fish can become so thin that the gut flora all but stops working and the fish can starve. Avoid buying anything with a concave belly, as these are not a safe bet.

A dark home will make a Starlight shine brightly (picture above by Johnny Jensen,
Ancistrus make for exciting biotope projects and lend themselves to wide ranges of set-ups.

Starlight bristlenose (Ancistrus dolichopterus) sometimes referred to as L183, are sublime for those wanting a colourful, easy to set up biotope for many community South Americans.

These are black water inhabitants from regions with slow flow. At just 10cm/4” fully grown and moderately inactive anything from a 60cm/2’ tank upwards will suit.

Water needs to be soft and acidic, so aim for a pH of between 5.0 and 7.0, preferably within the 6.0 range. Temperature can sit between 23-28°C/73-82°F, opening up a host of potential tank mate choices.

Go for light and fine sandy substrates and avoid any plants as these fish will not encounter any in their natural range.

Instigate heavy use of wood, plenty of fallen branches and fine tangles.

The Starlights will hide over and under the branches and make territories in makeshift wooden caves.

Use leaf litter heavily, for visual effect and also to help replicate the dark water, acidic conditions they thrive in. If unable to get hold of leaves, at the least use peat within the filter, or purchase proprietary blackwater extracts.  

Flow needn’t be huge, just serving to stir up leaves and sand.

Tank mates could be chosen from a monstrous list of sympatric Rio Negro fishes.

Carnegiella hatchet fish, Centromochlus macracanthus wood catfish and numerous Corydoras could happily fit into the surface and bottom layers respectiviely, and C. imitator, C. robinae and C. parallelus  are just a few suggestions.

Cichlid fans could opt for Dicrossus filamentosus to go alongside and the characin fan can stock up with Nannostomous pencilfish or stunning Cardinal or Green tetra. If you prefer your tetra more obscure, track down some Tyttobrycon xeruini for a real authentic feel.

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