Meet one of the few catfish that won’t stay at the bottom of your tank: the glass catfish. These fish are truly one of the most unique species available in the aquarium hobby due to their completely transparent bodies and free-swimming behavior. While they require more specific water parameters than most other beginner freshwater fish, the glass catfish can easily be kept if given some extra consideration.
Keep reading to find out everything you need to know about glass catfish care and keeping these fish in your own aquarium!
Kryptopterus vitreolus is commonly known as the glass catfish, ghost glass catfish, ghost catfish, or phantom catfish. Their species name, vitreolus, is derived from the Latin word for glass and was assigned for obvious reasons!
Kryptopterus vitreolus is an official member of the catfish order, Siluriformes, despite their free-swimming evolution. The Kryptopterus genus has 18 different species as of June 2020, and is known for housing a multitude of cryptic species (species that are very difficult to morphologically differentiate from each other due to similarities).
For years, Kryptopterus vitreolus was misidentified as Kryptopterus bicirrhis and Kryptopterus minor in the aquarium trade. We will discuss how to tell these species, among others, apart later in this article.
The glass catfish is mostly native to the southeast and coastal waterways of Thailand; they have not yet been observed in central Thailand. There have also been reported sightings of glass catfish in Penang, Malaysia, though the claim has not yet been scientifically verified.
Not too much is known about their natural environment although their range is quite limited. Glass catfish have mostly been collected from slow-moving or nearly stagnant brown- or black-stained waterways that are often high in turbidity.
Wild specimens are regularly collected for the aquarium trade and their environmental status has not been calculated; despite their popularity as an aquarium fish species, they have yet to be bred on a commercial scale.
The glass catfish is incredibly easy to tell apart from other fish, but incredibly difficult to tell apart from other members of Kryptopterus. So much so that for years, the glass catfish was misidentified in the aquarium trade as well as in scientific literature for a very long time.
These fish only grow to be about 2.5 inches (6.4 cm) long and are nearly completely transparent. This transparency is a characteristic of Kryptopterus and is due to a lack of body pigment. While they are catfish, they probably don’t look anything like the catfish that you’re used to seeing. They have long, tall bodies that display a good portion of their ribs and vertebrae; they also have some equally long and transparent barbels around their mouth.
At the transparent head of the glass catfish, most organs are able to be distinguished; the heart may sometimes even be seen under a magnifying glass. While these fish are clear, if they hit the light just right, they give off a brilliant display of iridescent rainbow.
There is no definite way to tell male glass catfish from females.
A long history of confusion
For nearly a century, the glass catfish was misidentified as other members of Kryptopterus, namely K. bicirrhis and K. minor. These fish resemble glass catfish in almost every way, and can easily be confused if not looked at carefully; the good news is that K. bicirrhis and K. minor have since been successfully identified and are hardly seen in the aquarium trade anymore!
K. bicirrhis. These fish have a larger natural range than glass cats and can be found throughout most fast-flowing river systems throughout southeastern Asia. K. bicirrhis is much larger than the true glass catfish, and can reach almost 6 inches (15 cm) in length. One of the major ways to tell these two species apart is by looking at the transparency of their bodies: glass catfish are truly transparent while K. bicirrhis has a cloudy/grey inner body.
K. minor. These fish are sometimes referred to as ghost catfish and can be harder to tell apart. Both K. minor and the glass catfish are relative in size and are transparent, however, K. minor is more native to only Borneo. The only way to truly tell these two fish apart is by looking at specific body features and measurements, including dorsal/dorsal fin profile, eye diameter, and snout length.
Even outside of the Kryptopterus genus, the glassfish is confused with other similar-looking species:
African glass catfish (Parailia pellucida).Unlike the previous look-alikes, the African glass catfish is regularly sold in the aquarium trade. Again, they are very similar to the true glass catfish, but are a little larger, growing to about 6 inches (15 cm). However, African glass catfish are native to most of western Africa and have more modified barbels that fall alongside the body of the fish.
Glass catfish tank requirements
Once you’re sure that your glass catfish is actually a glass catfish, how can you let your fish live its best life? Glass catfish are pretty small on their own but need to be kept in groups. This means that in order to keep an adequately-sized school of glass catfish, a 30 gallon (113.6 L) tank is recommended.
These fish really love a tank filled with live plants and natural hiding spots made out of rocks and driftwood. Floating plants are especially appreciated as these fish appreciate dimmer lighting; a low-intensity light will also help your fish be more active in the foreground of your tank. If you’re struggling with finding plants that can grow in minimal light, make sure to check out our 9 most useful low light aquarium plants here.
As these fish live in slow-moving to stagnant waters in the wild, water current should be minimal. Indian almond leaves and other plant detritus can also be added to help replicate their natural blackwater environments. While these fish tend to stay out of the lower water column, they could damage their barbels on larger gravel substrates; a more sandy and fine-grained substrate will keep your glass catfish injury-free!
The glass catfish can be a little more difficult to keep in an aquarium setting than other beginner fish due to their need for exact and stable water parameters. Any rapid changes in water chemistry or water temperature in your tank may cause your fish to quickly become stressed.
Ideal tank conditions are a stable water temperature between 75-80° F (23.9-26.7° C) and pH between 6.5-7.0; if using Indian almond leaves, make sure to regularly test water parameters in case pH drops due to tannins. Lastly, water hardness should remain between 8-12 KH.
Glass catfish tank mates
While glass catfish may be a little more difficult to take care of, they can still go with a whole assortment of freshwater tank mates and plants!
These fish get along with most other community fish. However, they do tend to be more on the shy side, so overly active and more aggressive fish should be avoided. Some recommended species are:
Tetras. For the most part, any kind of tetra will get along with your glass catfish! However, tetras are schooling fish as well and will generally need to be kept in groups of at least 6 or more. Some recommended species are: neon tetras, glowlight tetras, and cardinal tetras.
Swordtails (Xiphophorus hellerii). Swordtails are a favorite among beginner hobbyists due to their active behavior and variety of available colors. Growing to about 4 inches (10.2 cm), these fish need to be kept in groups where females outnumber the males. It should also be noted that swordtails are very likely to reproduce on their own without needing a separate breeding tank; if this happens, the fry should immediately be removed as glass catfish have been known to eat fry.
Harlequin rasbora (Trigonostigma heteromorpha). Harlequin rasboras are one of the most popular aquarium fish and make a beautiful contrast in any tank. They grow to about 2 inches (5 cm) long and will need to be kept in groups of 8 or more.
Dwarf gourami (Trichogaster lalius). If you’re looking for a centerpiece for your glass catfish tank then the beautiful metallic dwarf gourami might be the right tank mate for your school of glass catfish. They grow to about 3.5 inches (8.9 cm) and do best when kept in pairs. They need more established tanks and excessive commercial breeding has led to some health concerns.
How many glass catfish should I get?
One of the best tank mates you can get for your glass catfish is other glass catfish! These fish are naturally shy in the aquarium setting and become more active when kept with the same species. It is recommended to keep at least 6 or more glass catfish together.
A 30 gallon (113.6 L) aquarium will comfortably fit a school of 6 glass catfish. An additional 5 gallons (18.9 L) should be allotted for every additional member of the school.
Glass catfish behavior
Glass catfish are very peaceful fish that are relatively shy. These fish tend to form tight schools where they find safety in numbers. While they are shy, they do like to swim around the tank a decent amount. If they are stressed out, they will resort to hiding under aquarium decorations and in live plants; this may also be an indication that the lighting is too strong as these fish much prefer darker environments.
Unlike other species of catfish, these fish won’t live on the bottom of your tank. Instead, they favor the middle and upper water column. When idle, they tend to swim in a slightly angled position with their barbels facing the surface of the water.
Are glass catfish aggressive?
These fish are not aggressive at all! If anything, they are the first ones to get beaten up by more active and aggressive fish. If for any reason there are signs of aggression within the school, adding additional glass catfish may help (just make sure that you have the tank space to allow for an additional fish before adding one).
Glass catfish diet
Despite their peaceful nature, these fish are mostly carnivorous predators, meaning they will need a high-quality meaty diet. Luckily, their preferred food is smaller invertebrates and crustaceans, like zooplankton and fish fry.
What do glass catfish eat?
In the aquarium setting, glass catfish will need a large assortment of food with live, froze, and freeze-dried food options. A good diet will consist of worms (cut up earthworms, bloodworms, Tubifex worms, grindal worms), brine shrimp, and mosquito larvae.
While they are largely carnivores, glass catfish can be picky about their food. Some hobbyists have had success supplementing flake food while some fish completely ignore it. Even if your fish does accept flake food, meatier foods should still be the basis for the diet.
Breeding glass catfish
For the most part, breeding glass catfish within a tank setting is unheard of. It is widely believed that breeding coincides with the dry and wet season when water conditions fluctuate, especially water temperature.
If you are interested in trying to get these fish to breed, then it would be best to mimic those rainy season conditions in a breeding tank. Because it is not possible to tell the females apart from the males, it would be best to transfer a small group instead of just a pair of glass catfish. The aquarium should also be adequately planted to catch eggs; otherwise, an egg crate or mesh should be used to line the bottom to keep the fish from eating the eggs.
In this separate breeding tank, gradually lower the water temperature to the low 70s while adding small amounts of fresh water every day; this will attempt to replicate the rainy season. The fish should also be fed well during this time, with more high-quality foods and a larger assortment. If you’re lucky, the female will spawn her eggs. At this point, the adult fish should be placed back into the main display tank.
Within a few days, the eggs will hatch and the fry will become free-swimming. The fry may be fed small food, like cut-up brine shrimp and worms. The temperature should also be slowly returned to their preferred range of 75-80° F (23.9-26.7° C).
When the fry cannot be easily eaten by the adults, they may be transferred back to the main tank or given to another hobbyist!
For a fish that has had a long history of confusion, the glass catfish has maintained its status as one of the most well-liked beginner aquarium fish. These incredibly transparent fish are relatively easy to care for and look spectacular in a school. They are a little more susceptible to changes in water conditions than other beginner fish but can be readily introduced to more established systems.
If you have any questions about the glass catfish or have kept these fish in your own freshwater aquarium, don’t hesitate to leave a comment below!