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Glass Catfish

The Glass Catfish, Kryptopterus bicirris, is probably the most transparent fish in the aquarium hobby, less than 10% of its body (head, gut etc) being opaque, the rest being truly glass-like in appearance, to the point where one has to accustom oneself to looking for the head end in order to find the fish!

Glass Catfish are thus unusual, very interesting, but some caution needs to be issued. First, they have a very ounced need to be in a group of their own kind. Severe psychological stress will result if one tries keeping a lone specimen, stress sufficient to shorten the life of the fish considerably through it succumbing to opportunistic diseases as its immune system becomes depressed. With this fish, it is definitely a case of 'the more, the merrier', space allowing of course, which means that anyone contemplating buying these should first ensure that they have the space, and second, buy as large a group as possible. An ideal setup would see a dozen specimens in an aquarium furnished sensitively, under relatively subdued lighting, or if more intense lighting is used for plant growth, areas of shade provided by floating plants. Provide caves, bogwood arches and other hiding places for them, and ensure that any rocks that are used in their aquarium are smooth and rounded, with no jagged edges. This is particularly important with Glass Catfish, for reasons that will become apparent shortly. Likewise, it is a good idea to provide a kind of 'curtain' of reed-like plants such as Vallisneria around the back and sides of the aquarium, and again, this will be explained in a moment.

When purchasing Glass Catfish, watch closely as the dealer tries to catch them. The speed that they can achieve when trying to escape a net has to be seen to be believed! In a sprint race, this fish is the Carl Lewis of the aquarium, and can deliver explosive acceleration combined with uncanny manouevreability: anyone designing a submarine to match the prowess of this fish is assured a life-long career working for the military, I can tell you!

The trouble with all this darting about, is that they have a tendency to crash into objects if they don't detect them in time. Hence the Vallisneria curtain mentioned above: it acts as a 'crash barrier' and cushions the fish against undue impacts with the aquarium glass. Other furnishings should be chosen carefully with this facet of the fish's behaviour in mind, so that any bogwood should, if possible, be fairly soft and free of sharp edges. Between these various furnishings should be ample regions of open swimming space: preferably areas shaded by floating plants, to make them feel, if not exactly 'at home' (see below for more on their nervous disposition), then relatively comfortable.

In addition to racing about the aquarium to elude a net, Glass Catfish can, if they are 'spooked', jump. Quite a few textbooks neglect to mention this, but an article about these fishes by Linda Lewis in Today's Fishkeeper cautions prospective owners to keep a Glass Catfish aquarium securely covered, as they can launch into the air with an agility that is more usually associated with the likes of Hatchet Fishes!

Another response mentioned by Linda Lewis in her article, which manifested itself among her specimens, is the propensity of the fish to come to a sudden halt, flop over on one side or even upside down, and enter a kind of 'suspended animation' trance for an hour or more. When they do this, they can look dead with ease, and I suspect that this is a defence mechanism akin to 'playing possum', working on the basis that the predators they encounter in the wild are only interested in moving objects. After holding a position that looks disturbingly like the onset of rigor mortis for a period of time, they can suddenly 'snap back' into consciousness, as it were, and resume normal swimming activity as if nothing had happened. Be prepared for quirkiness of this kind in abundance when keeping Glass Catfish, as they are nervous and edgy even in supposedly ideal surroundings. While some fishes can he highly strung when introduced to a new aquarium, settling down later, Glass Catfish are like coiled springs throughout their lives, and can take it upon themselves to enter a panic for no apparent reason. Hence the careful attention to detail needed for their aquarium to avoid unpleasant accidents.

Once a group (minimum of six, twelve is much better - they resemble my Panda Corys in this respect) is safely housed, in the aforementioned carefully planned aquarium, the fun of feeding them begins. Persuading them to eat isn't the problem: what is more, they will avidly devour many offered foods, although if they can be conditioned with live foods for the first few days after introduction, this aids their 'settling in' enormously, always assuming that these edgy fish can ever be truly said to 'settle in' ... No, the problem is that Glass Catfish do not appear to see very well. Those long barbels should be a clue to the astute aquarist, that they locate their food prinicpally by touch and smell, so if they are housed with other fishes, ways and means have to be sought to make sure that the Glass Catfishes obtain their share of the food. Also, given that they tend not to like bright light, and that those long barbels can prove a little tempting to certain other fishes who like to nibble at anything even remotely worm-shaped, any companions should be gentle-natured ones, that don't bully the Glass Catfish away from the food. Even Guppies can prove overly boisterous companions to Glass Catfish, so fishes such as Tiger Barbs are definitely out!

When it comes to food, Glass Catfish can be persuaded to eat a wide variety of fare, but if there is one food that they do go completely nuts over, it is live Bloodworm. Feed them this on a regular basis and they'll be happy. However, make sure that they can find the Bloodworm when you add them! The same applies to other foods too: they can accept high quality flake foods, and finely ground beef heart with the fat removed is something of a treat for them, but remember, they frequently miss visual cues! Take note of where the currents in the aquarium are likely to carry morsels of food, and add food so that the Glass Catfish are 'downwind', as it were, of the sudden arrival of the manna from heaven!

The next aspect of Glass Catfish care to be aware of is this: longevity. When I made the comment in another post that 'a fish is for life, not just for Christmas', it applies to this species in spades. This is a species whose life span can exceed ten years if cared for properly, so before buying them, ask yourself if you are prepared to care for them for a decade or so. And remember that they might not take too kindly to frequent upheavals such as moving house during that ten years, so if you have itchy feet, Glass Catfish are probably not for you! While the species looks delicate, it can be hardy under the right conditions, and tolerate a fair spectrum of water chemistry parameters (provided that what comes out of the tap isn't extreme in some regard), but its preference is for neutral or very slightly acidic water, not too hard, but not necessarily very soft either: however, filtering over peat is reputed by some people to be beneficial to this species, although this is by no means universally accepted as necessary, and the question of filtering over peat will doubtless continue to be as much a matter of personal taste with this species as with many others.

Now, although the Glass Catfish is highly strung, can freak out in a frightening manner if it is upset, and go carpet surfing if 'spooked' and not securely covered, the good news is that given a sensitive owner and a carefully planned aquarium, its edginess becomes transformed into something more akin to bustling busyness. And, it can live happily in the aquarium for ten years or more. The bad news for many serious aquarists, looking at this gem during those moments when sunshine refracts through its body and sparkles with iridescent colour, is that thus far, no-one has successfully bred the species in the aquarium. At least, I have yet to hear of a successful account. So, a challenge is thrown open to the Glass Catfish keeper: be the first to breed it in captivity! And remember, if you, dear Board member, are that lucky first person, come here and tell us all about it, in exhaustive detail, so that we can all go out and replicate your success!




Panda Catfish fan and keeper/breeder since Christmas 2002

excellent article as usual calilasseia but i've got a question... i have read that glassies love a good flowing current, but i didn't read that in your essay? or are my books wrong?

cfd

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Billy was a scientist, Billy is no more. For what he thought was H20, was H2SO4

Yes, they do. In fact because they live in similar habitats, tiger barbs are actually reccomeded as tank mates for these fellars. Barbels are rarely eaten due to the electrical singals that run through them (or so many catfish experts have proposed). Furthermore, glasscats have rather bad vision and are therefore messy eaters. What they miss the barbs get.

Interesting read Cali.
I have 4 of these guys in my planted tank. (originaly had 6.... a story for another time) My aponogeton plant has taken off in a big way in that tank and the leaves provide a great shady area in the middle of the tank for them. As they have settled in they have become more adventurous and I often see them busily checking out the tank.
Interesting about their eyesight too. I wondered why they didnt go for food as much as the other fish.

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Before you criticize someone walk a mile in their shoes. That way you're a mile away and you have their shoes.

Yes, they do. In fact because they live in similar habitats, tiger barbs are actually reccomeded as tank mates for these fellars. Barbels are rarely eaten due to the electrical singals that run through them (or so many catfish experts have proposed). Furthermore, glasscats have rather bad vision and are therefore messy eaters. What they miss the barbs get.

Wasn't aware of this. Given some people's experiences with bositerous companions, I would have cautioned against Tiger Barbs, but if they're coeval, that puts a different complexion on matters.

Panda Catfish fan and keeper/breeder since Christmas 2002