Glass Catfish
Kryptopterus vitreolus
Min Tank Size
80L
Adult Size
8 cm
Lifespan
7 years
School Size
6+
About
Few fish stop people in their tracks like the glass catfish. Native to flowing rivers and streams in Thailand and surrounding parts of Southeast Asia, Kryptopterus vitreolus is almost completely transparent. You can see the spine running the length of the body and the small cluster of organs just behind the head. It sounds gimmicky but in person, especially under good lighting, it's genuinely stunning. A school of these hovering in the midwater column, slightly tilted into a gentle current, looks almost otherworldly.
They're not the easiest fish to keep, and that's where a lot of beginners run into trouble. Water quality needs to be consistently good. They don't tolerate spikes in ammonia or nitrite and they react badly to sudden parameter shifts. A soft to moderately hard setup with a pH between 6.5 and 7.5 and temperatures in the mid-20s Celsius suits them well. They prefer some flow in the tank, something that mimics the rivers they come from.
Diet-wise, they're carnivores that do best on live or frozen foods. Baby brine shrimp, daphnia, and bloodworms are all accepted. Getting them onto dry food can be done but takes patience, and some individuals never fully commit to it.
Temperament is entirely peaceful. They don't bother other fish, they don't dig, they don't touch plants. What they do need is the security of numbers. A group of fewer than six will become reclusive and stressed. Six or more and they'll hold position in the water column, swaying together in the current, which is exactly what you want to see.
If you're curious what a working glass catfish tank actually looks like, browsing community builds from other hobbyists can give you a real sense of how they're being kept successfully.
Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Glass Catfish together
Glass Catfish are shoaling fish and need company of their own kind. Keep a group of at least 6. Smaller groups leave them stressed, washed-out in color, and prone to hiding.
Compatibility
Good tankmates are calm, similarly sized fish that won't nip. Harlequin rasboras, ember tetras, small danios, and peaceful corydoras on the bottom all work well. Avoid tiger barbs, serpae tetras, or anything with a reputation for nipping, because those trailing fins will get shredded fast. Larger peaceful cichlids like rams can coexist if the tank is spacious enough, but it's a judgment call. Small ornamental shrimp like neocaridina are technically possible, but the catfish may pick off shrimplets, so that's a risk to weigh. Snails are completely fine. A 100-liter or larger tank opens up more stocking options and keeps the school comfortable.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The biggest mistake people make is adding these to a tank that's too new or too unstable. They need a fully cycled, well-established setup before they go in. Secondly, people underestimate the group size requirement. Three or four fish hiding in a corner is not a school, it's a stressed cluster waiting to decline. Get six minimum, preferably more. Feeding is another sticking point: if you're only offering dry flake, they may slowly starve. Frozen or live small foods should be a regular part of their diet. Keep the current going and the water clean, and they'll reward you with some of the most unusual midwater behavior in the hobby.
Behavior & Aggression
Glass catfish are about as non-aggressive as freshwater fish get. They don't establish territories, they don't chase tankmates, and they have no interest in harassing other species. The only thing resembling conflict you might see is mild jostling within the school itself during feeding, which passes quickly. They are absolutely not a threat to any fish, snail, or plant. The aggression concern runs entirely the other way: they are a target, not a threat.
Things to Know
- Extremely sensitive to water quality, do not add to immature tanks
- Groups smaller than 6 will hide constantly and decline from stress
- Avoid any fin-nipping tankmates, their long trailing fins are a target
- Need gentle to moderate current to feel at home and stay visible
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