Fish Profile: Thai Glass Catfish

Say hello to Kryptopterus minor, the "Thai Glass Catfish", whose natural range includes Thailand, Malaysia, and Indonesia, so "Southeast Asian" Glass Catfish might have been a better name. As the name suggests, these apparently-transparent fish are Siluridae... proper catfish.

For once, common names get it right in two ways - firstly, K. minor is actually transparent. This is not an illusory property of iridescence, but an actual question of their nature - the bits of them that can be seen are their proper internal organs and bones. This transparency has most to do with the small size of their body, their lack of pigmentation, and, being Siluridae, their lack of scales - when they die, the processes involved in decomposition very quickly turn them a milky white.

This scaleless property makes them somewhat sensitive - accordingly, it's very important to maintain proper water quality. While this is not difficult, their quirks, this included, serve to place them squarely in my "not for beginners category". They prefer cooler water by tropical standards - between 21 and 26 degrees Celsius (most fish would prefer several degrees warmer than that), which should be as soft as is possible, and within a relatively narrow range of pH 5.5-6.5. Soft, acidic water is acceptable for those building community tanks, and this species has no real problem with that, though there are some considerations which I will detail in a moment.

In addition to being rather chemically sensitive, this Siluriform has some interesting behaviour traits. For one thing, and in my view, somewhat unusually for their group of fish, these are absolutely schooling fish - groups of six or more are necessary, otherwise the fish get locked into what I can only describe as "pining mode" and will lose all appetite even to the point of starving to death. Even if they are eating, elevated stress hormone levels made them even more sensitive to contracting illnesses. Plan accordingly - if a glass catfish isn't going to be the feature of your tank, make the feature fish something passive that will leave room enough for your 6+ school of glass cats.

Having said that, most recommendations for tank mates are smaller animals - rasboras, peaceful tetras, the smaller anabantoidei (such as Dwarf Gouramis), and chemically suitable dwarf cichlids - care will have to be taken in the latter case when it comes to finding overlapping pH bands that are suitable.

They appreciate a high flow rate (which, if done properly, would only improve filtration and water quality), with floating foliage to keep the light diffuse and dim (as is preferred by them). Breeding is almost unknown in aquaria, but know to be seasonal - best guesses on triggering breeding behaviour involve lowering the tank temperature and heavy daily water changes. Accordingly, most specimens are wild-caught.

They're somewhat picky eaters - small, protein-rich flake is often accepted (such as Nutrafin Max Staple Diet), though they frequently accept live and frozen versions of brine shrimp, blood worm, and daphnia.\

All told, they're a nice fish when you can find them. We have them presently (as of the time of writing) at my store for $15.78 retail, with all sorts of fun specials and quantity discounts... but I've been working there for six months and this is the first time I've seen them.