What to Know About Glass Catfish

Medically Reviewed by Vanesa Farmer, DVM on January 05, 2023
4 min read

Glass catfish get their name because they look like they’re made of glass. These fish are see-through! Their clear bodies allow you to view their bones and organs. This unique feature makes them popular aquarium pets.

Glass catfish, also called ghost catfish or phantom catfish, are a group of species in the catfish genus Kryptopterus. While this genus has multiple species, only three of the species found so far have clear bodies that qualify them to be called glass catfish:

  • Kryptopterus minor
  • Kryptopterus piperatus
  • Kryptopterus vitreolus

For a long time, especially in the pet trade, a species called Kryptopterus bicirris were often mistaken for Kryptopterus vitreolus

The key difference between these species is that while the body of K. vitreolus is completely clear, only the area near the head of K. bicirris is clear. It’s likely that most glass catfish in the aquarium trade that were once labeled K. bicirris are or were K. vitreolus.

The clear appearance of K. vitreolus and the other glass catfish is what makes them so fascinating. Their bodies are completely see-through. This allows you to see their organs, bunched up by their heads, and their spines. You can even see their heart beating with a magnifying glass.

No species of catfish has scales, and that includes catfish in the Kryptopterus genus. But what makes these catfish transparent is their lack of pigmentation as well. 

Unlike other types of catfish, their skin cells don’t carry color. They’re completely clear. It’s not known exactly why this is, but when glass catfish die, they become a milky white color, indicating that maybe something the catfish does while alive produces the cells.

Like most other species of catfish, glass catfish have barbels, the “whiskers” on their heads that give the catfish their name. These barbels are used as feelers to find food, and on glass catfish they are completely clear like the rest of the body. 

The fins of the glass catfish are also see-through. Glass catfish have an anal fin, or a fin that runs along the underside of their body. This fin runs from their head to their dorsal fin, or tail fin, which is forked. Another feature that sets glass catfish apart from other types of catfish is their lack of a dorsal fin, a fin that runs along the top of the fish. In fact, this is where the genus name comes from. Kryptopterus is Greek, with the root ‘kryptos’ meaning hidden and ‘pterus’ meaning fin. Kryptopterus means “hidden fin.”

Glass catfish size can vary wildly between the species. Kryptopterus vitreolus usually grows to about 3.1 inches (8 centimeters), while Kryptopterus minor reaches about 2.7 inches (6.8 centimeters) on average. Kryptopterus bicirrhis, the fish that K. vitreolus was often mistaken for, can grow much larger, an average of 5.9 inches (15 centimeters). 

It’s almost impossible to tell male and female glass catfish apart. The only difference is the males are usually slightly smaller than the females.

All species in the genus Kryptopterus are found in freshwater habitats in Southeast Asia. The exact location depends on the species.

  • Kryptopterus minor is found mainly in Indonesia.
  • Kryptopterus piperatus is typically found within forest rivers with a moderate current in Indonesia, especially the Alas River and Lembang River.
  • Kryptopterus vitreolus is found throughout the peninsular and southeastern areas of Thailand, usually in slow-moving or standing murky water. There have been reports of sightings in Malaysia, but those are yet to be verified.

While many species of catfish are bottom feeders that keep to the river floor, glass catfish often prefer to swim in the middle of the water. This is another reason they’re a popular aquarium fish, as they’re much more active than other species of catfish.

In the wild, glass catfish mostly eat very small fish or small invertebrates such as:

  • Mosquito larvae
  • Tiny crustaceans, like water fleas (genus Daphnia)
  • Zooplankton

On average, glass catfish live about six to eight years.

There isn’t much information known about the life cycle or breeding practices of glass catfish. Glass catfish are very difficult to breed in captivity.

Thanks to their unique look, glass catfish, especially Kryptopterus vitreolus, are a popular freshwater aquarium fish. They’re also relatively easy to look after, so long as you provide them what they need.

Tankmates. Glass catfish normally travel in groups, called schools. As a result, they need to be around other fish. They should be in schools of at least three to six.

Glass catfish are generally peaceful fish. If you’re keeping them in a tank with other fish, they need to be with species that are peaceful and not too large.

Tank and water. For a group of five or so glass catfish, they should be in a tank that’s at least 30 gallons. The more fish you have, the larger the tank needs to be. Their tanks should have both open areas and hiding spots. Some of the best things to keep within their tank are plants that create cover, rocks, and other ornaments.

While glass catfish aren’t difficult to care for, they do require certain water parameters. This includes:

  • Hardness level between 8-10 12 degrees of general hardness (dGH)
  • pH between 6.5-7.5
  • Temperature between 75-80°F (24-26.7°C), although they can survive in temperatures between 72-82°F (22.2-27.8°F)

The water in the tank should have a medium flow to it.

Diet. In the wild, glass catfish mostly eat very small fish or small invertebrates. When keeping pets in an aquarium, you should try to imitate their wild diet as closely as possible. Daily pellet or flake food is important and will provide the basic nutrients for your fish. For added protein, you can also offer your glass catfish: 

  • Bloodworms
  • Brine shrimp
  • Grindal worms
  • Tiny crustaceans like Daphnia
  • Zooplankton such as Moina

Glass catfish are low-maintenance fish aside from their narrow water parameters. They’re also fascinating to look at, and can make an excellent addition to a freshwater aquarium.