Glass Catfish Care Guide

The glass catfish is the transparent fish you can watch breathe — its backbone and beating heart show through a body of living glass. It is an obligate shoaler and a sensitive one, so the two facts that decide whether it lives are simple: never keep fewer than six, and never treat it as a bottom-cleaning scavenger, because it is a mid-water feeder that will quietly starve on leftovers.

Glass Catfish at a glance

The sourced figures the welfare engine uses to judge Glass Catfish — the parseable key facts.

Where it comes from

The trade fish is Kryptopterus vitreolus, formally named only in 2013 by Ng and Kottelat after roughly eighty years of being misidentified — for decades it was sold as the larger, opaque, solitary K. bicirrhis, and later as the Bornean K. minor, and both names are legacy misnomers you will still see on shop tanks and old care sheets. If a label says bicirrhis or minor, size and temperament copied from those sources do not apply to your fish. It comes from slow and standing waters of peninsular and south-eastern Thailand — sluggish streams, backwaters and shaded pools, in turbid brown to acidic blackwater. That origin sets the care: soft, slightly acidic, low-mineral water, tannins and dim light, gentle flow, and a well-planted tank that still leaves an open mid-water lane for the school to hover in.

Did you know?

• You can watch its heartbeat and see its skeleton — the body is transparent enough that the backbone and a beating heart show through, hence 'glass', 'ghost' and 'X-ray' catfish.
• The transparency is a light trick: a 'plywood-like' lattice of collagen fibrils lets light pass and diffract through the muscle, giving a faint iridescent rainbow at the right angle.
• It went eighty years without a name — one of the most-kept aquarium catfish was misidentified as K. bicirrhis or K. minor until Ng and Kottelat formally described it as K. vitreolus in 2013.
• It is a catfish that lives in open mid-water and won't touch the bottom — the opposite of the bottom-dwelling catfish stereotype.
• It tells you when it is unhappy by going cloudy — a built-in, visible stress gauge most fish don't have.
• Conservation status is IUCN Least Concern (assessed 2019), but being wild-caught-only from a small Thai range raises real sustainability questions as trade volume grows.

Tank size — and why

Twenty US gallons is the absolute minimum for a group of six, but about 30 gallons is the recommended floor and the better choice. The driver is not bioload — this is a small, low-waste fish — it is room for a real shoal to school in open mid-water and, just as important, the water-volume stability that a swing-sensitive species depends on; parameters stay steadier in a larger tank. Prioritise length and open swimming space over height: this is an active mid-water swimmer, not a hider.

As a guide, a 30-gallon tank comfortably suits about 8–12 Glass Catfish as a single-species display, leaving room for tankmates.

How big does it really get?

Full-grown Glass Catfish reach about 6.5 cm (2.6 in) long, but they are usually sold at only about 2.5 cm (1 in) — a typical shop size (estimate). At full size, Glass Catfish needs roughly a 30-gallon tank, about 76 cm long; a common 10-gallon starter kit is only about 51 cm.

Adult size is sourced; the shop size is a typical-juvenile estimate; tank length is approximate for a standard 30-gallon aquarium.

Water parameters in practice

Stability beats hitting an exact number — this is the load-bearing point. Keep it in soft, slightly acidic water at around pH 6.0–7.0 (it tolerates down to about 4.0; ignore the lone source pushing the ceiling to alkaline 8.0, which conflicts with its blackwater origin) and soft hardness of roughly 3–10 dGH. Temperature of about 23–26 °C suits it, with tolerance across 20–27 °C. The species is genuinely susceptible to swings in water chemistry and should never go into a biologically immature tank: aim for zero ammonia, zero nitrite and low nitrate, then hold it rock-steady. Most early deaths are husbandry-caused, not exotic disease.

Diet & feeding

This is where most keepers go wrong. It is a mid-water micropredator, not a scavenger — it takes food drifting in open water, and anything that falls to the bottom is rarely picked up, so relying on it to clean up leftovers slowly starves it. Feed small, slow-sinking or suspended foods in open water, ideally small live and frozen fare such as baby brine shrimp, daphnia, moina, cyclops, bloodworm and grindal worm; good micro pellet or flake can be accepted, but live and frozen drive condition. Feed small amounts once or twice a day, and because the timid school is easily out-competed by faster fish, target-feed it or feed when tankmates are occupied so the group actually eats.

Gear & setup

Set it up for a shaded, slow-water biotope: gentle flow, densely planted edges with floating plants for shade, driftwood and leaf litter for tannins, and a soft, dark substrate that shows off the transparency — all leaving an open mid-water lane for the school. Dim conditions reduce stress and bring out natural behaviour, while a bare, bright tank causes constant hiding. Fit a lid, as glass catfish can jump, especially when startled. Because it is a scaleless catfish, treat illness cautiously — copper and some formalin-based medications are best dosed scaleless-safe or at reduced strength.

Temperament & behaviour

Peaceful, shy and highly gregarious, forming quite tight schools when kept properly. It shows no territorial behaviour, does not nip and has no intraspecific aggression; the risk runs the other way, as it is easily bullied and out-competed by boisterous tankmates. A big group in a planted, dim, gentle-flow tank gives you a clear, confident school hovering in the open. The same fish in small numbers loses its schooling behaviour, becomes reclusive, fades towards opaque and stops eating — its mood is written on its body.

Group & social needs

An obligate shoaler — six is the hard, non-negotiable floor and eight to ten or more is the real target. Keeping it singly, in pairs or in threes is the signature lethal failure: solitary fish hide constantly, lose transparency and die of chronic stress within weeks. As one care source bluntly puts it, a group of three is not a school, it is a countdown to dead fish. Never buy singles or pairs.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Glass Catfish and that suit its size and temperament best. Tap any to load the pairing in the planner.

• Amano Shrimp — Peaceful temperament, similar adult size.
• Bamboo Shrimp (Wood/Fan Shrimp) — Peaceful temperament, similar adult size.
• Black Neon Tetra — Peaceful temperament, similar adult size.

A note on the shrimp and snails here: Glass Catfish is peaceful and generally invertebrate-safe — but almost any fish will take very small shrimplets given the chance, so give shrimp dense cover (moss, leaf litter) if you want a colony to grow, rather than expecting every baby to survive.

This engine-cleared shortlist is Glass Catfish's tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Effectively not a home-breeding fish. Seriously Fish records breeding as unrecorded, and hobby sources call captive spawning extremely rare with no reliable, repeatable protocol. Sexing is subtle and poorly documented — some reports note ripe females showing a rounder abdomen — but treat it as uncertain. Because the fish is essentially not bred in captivity, the aquarium trade relies on wild-caught specimens, which raises real sustainability questions given its limited Thai range and high export volume.

Lifespan

Roughly 5–8 years in a stable, mature tank, with about 5 more typical in an average setup and 7–8 achievable with steady, well-kept water. What shortens it, in order: too small a group, unstable or immature water, starvation from being treated as a scavenger, bright exposed tanks with no cover, and being added to a brand-new uncycled tank.

Common mistakes

• Buying one to three fish. The signature, fatal error — buy six or more, ideally ten or more, or don't buy at all.
• Treating it as a scavenger or bottom cleaner. It is a mid-water feeder; relying on it to eat leftovers starves it. Target-feed in open water with small live or frozen foods.
• Adding it to a new, uncycled or unstable tank. It is swing-sensitive and needs a mature, established aquarium.
• Bright, bare, high-flow tanks. These cause constant hiding and stress — provide dim light, planting, floating cover and gentle flow.
• Boisterous or predatory tankmates. Tiger barbs and serpae tetras stress it and steal its food; large or aggressive fish will eat a 6 cm soft-bodied fish.
• Trusting 'K. bicirrhis' care sheets — that old size and temperament data is the wrong species; your fish is K. vitreolus.
• Buying clouded or opaque stock. A milky glass catfish is stressed or sick; choose clear, actively-schooling fish.

Signs of trouble

• Loss of transparency — turning milky, cloudy or white is a primary distress signal, not a colour change.
• Leaving the school, hiding and isolating itself.
• Refusing food and a clamped, hunched posture.
• Rapid breathing, often pointing to a water-quality problem.

Is this fish right for you?

Don't buy it if you can't keep a group of six or more, if your tank is new or unstable, if your water is hard and strongly alkaline and you can't soften it, if your community has nippy, large or aggressive fish, or if you wanted a self-cleaning catfish — this is emphatically not one. Keep it only with calm, peaceful, non-predatory tankmates its own size or smaller. Essentially all trade stock is wild-caught from a limited Thai range, so buy healthy, well-acclimated, clear imports, quarantine them, and never buy dyed or 'painted' specimens.

Common questions

How many glass catfish should I keep?

Six is the hard minimum and eight to ten or more is ideal. It is an obligate shoaler, and kept singly, in pairs or in threes it stops schooling, hides, turns opaque, stops eating and dies of stress. Never buy singles or pairs.

Why is my glass catfish turning white or cloudy?

Loss of transparency is a primary stress or illness signal — usually too small a group, unstable or poor water, or a brand-new tank. Check the group size and water parameters, and make sure it is in a mature, stable, dimly-lit planted tank.

Is the glass catfish a bottom feeder or scavenger?

No — this is the most damaging myth. It is a mid-water feeder that takes food from the water column, and food that sinks to the bottom is rarely eaten. Feed it actively in open water with small live or frozen foods, or it slowly starves.

Are glass catfish good for beginners?

Not really. It is sensitive to chemistry swings and intolerant of immature tanks, and it needs a real group plus active mid-water feeding. Keep it only in a mature, stable, cycled tank, which is why it is not a true starter fish.

What is the difference between Kryptopterus vitreolus and K. bicirrhis?

The transparent, schooling aquarium fish is K. vitreolus, named in 2013. True K. bicirrhis is a larger (~10–15 cm), opaque, solitary species rarely seen in shops. If you can see the skeleton, it's vitreolus; bicirrhis and minor on a label are legacy misIDs.

Sources & confidence

Sources & confidence (9 species)

These back the Glass Catfish figures and the previewed tank mates above. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

• Glass Catfish Kryptopterus vitreolus — Seriously Fish (seriouslyfish.com/species/kryptopterus-vitreolus); Aquariadise high confidence
• Amano Shrimp Caridina multidentata — Aquarium Co-Op amano shrimp care; Aquadiction high confidence
• Bamboo Shrimp (Wood/Fan Shrimp) Atyopsis moluccensis — Aquariadise (aquariadise.com/caresheet-bamboo-shrimp-atyopsis-moluccensis) high confidence
• Black Neon Tetra Hyphessobrycon herbertaxelrodi — Seriously Fish / Aqua-Fish (Hyphessobrycon herbertaxelrodi) high confidence
• Black Phantom Tetra Hyphessobrycon megalopterus — Seriously Fish (Hyphessobrycon megalopterus) high confidence
• Boesemani Rainbowfish Melanotaenia boesemani — Seriously Fish; Aquarium Co-Op Boesemani guide high confidence
• Bolivian Ram Mikrogeophagus altispinosus — Seriously Fish (seriouslyfish.com/species/mikrogeophagus-altispinosus) high confidence
• Brilliant Rasbora Rasbora einthovenii — Seriously Fish (seriouslyfish.com/species/rasbora-einthovenii) high confidence
• Bristlenose Pleco Ancistrus sp. — Aquarium Source / aqua-fish.net Ancistrus care guides high confidence

Care-guide sources (7)

This guide synthesises the references below; where they disagree, the range and the disagreement are noted in the text above. The figures in the key-facts box are read from the TankStocking species database (v2026.06). Full welfare model on the methodology page.

• Seriously Fish — Kryptopterus vitreolus — authority (Ng & Kottelat 2013), family Siluridae, bicirrhis/minor taxonomy, peninsular Thailand range, slow/standing brown & blackwater habitat, 55–65 mm SL, temp 20–26 °C, pH 4.0–7.0, GH 18–179 ppm, 'highly gregarious / tight schools', 6+ group, 'susceptible to swings in water chemistry', not for immature tanks, dim/leaf-litter setup, sexing unknown, breeding unrecorded
• Ng & Kottelat 2013 — 'After eighty years of misidentification, a name for the glass catfish' — formal description (Zootaxa 3630(2): 308–316), diagnostic features, distinction from K. bicirrhis and K. minor, etymology (vitreolus = glassy), Thai range, the 80-year misidentification history
• FishBase — Kryptopterus vitreolus — authority (Ng & Kottelat 2013), family Siluridae, max 6.5 cm SL, 'slow moving to standing, brown to black, water', peninsular & SE Thailand, trophic level 3.6, IUCN Least Concern (2019)
• Wikipedia — Glass catfish (Kryptopterus vitreolus) — Ng & Kottelat 2013, 'until 1989 considered the same as K. bicirrhis', ~6.5 cm TL up to 8 cm, transparency mechanism (plywood-like collagen fibrils), visible skeleton/heartbeat, Thai endemism, trade 'generally relies on wild-caught specimens'
• AquariumBreeder — Glass Catfish care guide — 6–8 cm, lifespan up to 5 yr, ~20 gal (80 L) for 6–8, temp 22–26 °C, GH 3–15 dGH, mid-water feeder ('food that falls to the bottom is rarely picked'), min group 6 (10+ better), loses transparency when alone, ammonia/nitrite/nitrate intolerance, jumping/lid, breeding extremely rare (pH→8.0 ceiling treated as outlier)
• AquariumStoreDepot — 'Glass Catfish: The See-Through Fish That Schools or Suffers' — ~2–3 in, lifespan 7–8 yr, ~30 gal, temp 75–80 °F, pH 5.9–7.0, not a bottom scavenger, min group 6 ('a group of three… a countdown to dead fish'), 'lose schooling behavior, become reclusive, stop eating', 'sensitive to parameter swings and stress', not for beginners
• AquariumSource — Glass Catfish Care — lifespan 7–8 yr, ~30 gal for a school, temp 75–80 °F (77 optimal), pH ~6.5, GH 8–10 dGH, mid-water active swimmer (not scavenger), group 5+, solitary fish in 'constant state of stress', strict-parameter sensitivity, breeding 'not done very often' (the '4–6 inch' size figure rejected as a bicirrhis conflation)

More on Glass Catfish

Related guides on TankStocking — each scored by the same welfare engine as the planner.

This care guide is a sourced planning reference, not veterinary advice — individual fish, filtration and maintenance all matter. Cycle the tank, test your water, and observe your fish. How TankStocking works →