Asian Glass Catfish: A Transparent Fish
This see-through fish from Borneo (Indonesia), in common with many other tropicals kept in the hobby, suffers from name confusion on both its common name, the Glass Catfish, but also sometimes the Ghost Catfish, as well as of its scientific name, Kryptopterus minor, but most often it is listed as Kryptopterus bicirrhis. The latter common and scientific names actually apply to a larger close relative which likely only very rarely if it ever has been in the hobby trade. So we are likely to buy the fish as K. bicirrhis, but it is really K. minor. It does seem to be called The Glass Catfish most often in the trade these days. It really is better to specify it as the Asian Glass Catfish, as there are African catfish also called Glass and/or Ghost catfish. We really do mess up our fish names constantly and continuously.
The eye-catching things about these fish are the fact that they appear to be transparent – their skeleton is visible for most of the body length – and the almost invisible solid muscle and skin appear clear with an iridescent surface which catches the light with flashes of color from their all-but-constant gracefully swimming motions, even when they are holding stationary in the water. In some live-bearers, that motion might be called “shimmying”, but this the normal “rest” or “hover” motion of these fish. Their internal organs are held immediately behind the head in a mirror-surfaced pouch or cover. They have a pair of very long barbels, commonly held forwards, which are about the length of the body in appropriate care set-ups.
These Glass Catfish are relatively easy care fish, but are delicate in a few ways. They are obligate schooling fish and should not be kept in groups of fewer than four fish, and will be much better in groups of twice that number or more. For me these fish show their unhappiness in small groups by swimming less and dying young. They also should not be kept with boisterous or aggressive fish of any sort. Stress keeps them stationary in the plants, and shortens their lives markedly. These are bashful and relatively short-lived fish in most conventional mixed tanks. They will do okay in mixed tanks with the smaller Rasboras (R. heteromorpha is fine with them in my experience). The small Tetra schooling fish are also expected to be okay companions. But I can only confirm that myself for Neon, Cardinal, or Lemon Tetras. They only Barb I have kept successfully with these catfish are the Cherry Barbs (Puntius titteya), and that was with a school of six males (in male-only schools these Barbs maintain breeding color constantly, and keep their attentions to their own kind). They are also pretty good with the smaller Cory catfish species. I had a school of 12 of these cats with the six male Cherry Barbs mentioned before and 12 Corydorus arcuatus, plus three Otocinclus catfish in a heavily planted 55 gallon tank which was spectacular enough to please my wife. That is no small thing. It was also simple enough to not offend me – the fish all kept to themselves, largely ignoring their co-housed other fishes. I really prefer species tanks myself, with a few “workers” or ‘helpers” as needed with all attention focused on a specimen fish or a mated pair or a single school. If I were to re-set that tank today I would likely add Red Cherry shrimp in the hopes that the Glass catfish would harvest enough small shrimp fry to meet their live food needs. I might have to omit the Cherry Barbs to avoid competition for that live food supplement.
In the wild, these fish are from soft acid water along the edges of rivers and in theory might do best in such water in captivity, but I do not set such tanks other than for breeding low-GH (general hardness or calcium and magnesium hardness) fish. I am only willing to do water modification when absolutely necessary for breeding. As these catfish have not been reliably captive-bred even with such water conditions, I do not bother. Schools of the these catfish for me still live 6-10 years on the average, the shorter average number from the presence of tankmates, the longer as specimen schools plus helpers only. That comes down to be a personal-choice item.
These catfish will survive well on a good selection of high-quality smallish flake foods and the smallest floating pellet foods without any small frozen/thawed or live foods added to the diet. But they will do better with some regular or frequent small live food added. In the wild it appears that their diet primarily is small aquatic insects. Freshly hatched and rinsed baby brine shrimp are taken, so if you are hatching such for other fry-feeding, any excess can go to these fish. If not, you might try co-culturing Red Cherry shrimp or adding a refugium allowing the shrimp fry to be passively moved to the display tank with these fish. The Cherry Barbs, if used in the same tank, will get the lion’s share of such live food.
These fish really, really need live plants to be most secure. I use end and background Vallisneria spilalis, with a carpet of Anubias nana and or Anubias petite, and a clump or two or three of colorful Cryptocoyne (such as some of the many C.wendtii cultivars). If the Val does not have the length to provide at least 50% surface cover initially, I add “Water Sprite” (a.k.a Indian fern, Ceratopteris thalictroides) floating until the Val develops enough cover, then I remove that plant as no longer needed for the security of the catfish. If you opt for artificial plants, at least add sufficient “Water Sprite” to provide cover at the surface.
Although tropical, these catfish do not need very warm water. 70-79F is a good range for them. Anything significantly higher is likely to make these a delicate fish, which they are not in the proper temperature range. Not all tropical rivers are warm, quite a few SE Asian rivers are coolish due to altitude.
These catfish also need some currents. It should be stronger out in the open or foreground areas; gentler in the planted corners and back for resting in the school among plant cover.
When gravelly ill or dying, these fish lose their transparency to become opaque white. Then the name “ghost” would be more apt for them.
Aquarium upkeep is routine. The usual 50% partials weekly, coupled with frequent mechanical filter rinsing and a mature biofilter is required. With moderate lighting levels as I use [approximately 2WPG (watts per gallon) NO (normal output) full spectrum fluorescent light, 9-12 hours per day lighted, on timers]. The Val will need thinning periodically, or at slightly longer intervals (~ 1 year) removal, substrate full-depth vacuuming and replanting at much less than harvest density). The Crypts and Anubias only need thinning or pruning attention every 2 or a bit more years.
A species set-up (one school of fish plus perhaps some “helpers” or upkeep crew) may be housed in a 30 or 40 US gallon long style tank. Mixed tanks with a school of these fish would be better in a 55 or even a 75 US gallon tank.
These are spectacular showpiece schooling fish in a basically species tank, or when co-housed with non- threatening smallish fish groups. For those not new to planted tanks, these fish offer the chance to set a low-upkeep easy care planted tank set to showcase a relatively common fish which is only rarely seen in a tank where it can be active and as showy as it should be. Those not yet proficient at planted tanks will find set-ups such as that described in this note relatively easy introductory tanks, but Anubias nana is not inexpensive, although it lives forever. For those who are susceptible to MTS (multiple tank syndrome) these fish may be dangerous – they feed your condition by showcasing this common fish exactly the way it should be seen but so rarely is – that leads to all sorts of other special specimen display or schooling tanks. Caveat emptor!
Robert T. Ricketts, Jr. a.k.a. RTR