Glass Catfish Care Guide: Tank Setup, Diet & Tank Mates for Kryptopterus vitreolus

Species Overview#

Glass catfish (Kryptopterus vitreolus) are the rare aquarium fish that looks engineered rather than evolved. The body is genuinely transparent — you can see the spine, the swim bladder, and the silvery coffin-shaped sac that protects the internal organs, all framed by a faint iridescent shimmer. A small school drifting in mid-water under subdued light is one of the most striking displays in the freshwater hobby, and it costs roughly the same as a handful of tetras.

The catch is that this fish does not behave like other catfish. It does not sit on the bottom, it does not eat sinking pellets at midnight, and it absolutely cannot be kept alone. Glass catfish are mid-water schooling fish that face directly into the current, hover almost motionless for hours, and need a group of at least six to behave normally. Get the schooling and water stability right and they live 7-8 years. Get either wrong and they typically die within weeks of purchase.

Adult size

3 in (7-8 cm)

Lifespan

7-8 years

Min tank

30 gallons (school of 6+)

Temperament

Peaceful schooling

Difficulty

Intermediate

Diet

Carnivore

Natural Habitat#

Kryptopterus vitreolus comes from the slow-moving rivers and forest streams of southern Thailand and the Malay Peninsula, not the larger river systems often credited in older sources. These waters run shaded under canopy, are slightly acidic and soft, and carry tannins from leaf litter that tint the water and dim the light reaching the substrate. Flow is gentle — these fish do not live in whitewater — and the water column is the part of the habitat they actually use.

Replicating this means soft, slightly acidic water (pH 6.5-7.0), subdued lighting, dense planting, and a dark substrate. Bright, bare tanks washed out with strong overhead light will keep glass catfish alive but will also keep them stressed, hiding, and dull-looking. Their transparency reads best against a dark background with diffused light filtering through plants.

Appearance & the "Glass" Effect#

The transparency is the entire point of the species. Light passes through the muscle tissue, leaving the spine, ribs, and a small reflective organ pouch (the silvery sac near the head) clearly visible from across the room. There is a faint pearlescent shimmer along the flanks at certain angles, but no scales, no bold pattern, and almost no visible internal coloring beyond the organs themselves.

The most common identification mistake in the hobby is confusing Kryptopterus vitreolus with Kryptopterus bicirrhis. The latter is also called "glass catfish" or "ghost catfish" in older literature and grows to 6+ inches — twice the size. K. vitreolus is the species that actually shows up in the trade today and stays around 3 inches. If a store labels a fish as glass catfish but the adults in the display tank are pushing 5 or 6 inches, you are looking at K. bicirrhis, which needs a much larger tank.

This species is also commonly sold under the name "ghost catfish" — same fish, different label. See our ghost catfish guide for additional notes on naming and sourcing.

Size & Lifespan#

Adults reach roughly 3 inches at full maturity. With stable water and a properly sized school, they routinely live 7-8 years in captivity, which is significantly longer than most fish in their price range. Premature deaths almost always trace back to one of four causes: shipping stress without proper acclimation, schools too small, copper-based ich treatment, or fish-in cycling.

Water Parameters & Tank Requirements#

Glass catfish forgive almost nothing about water quality. They tolerate a reasonable range of stable conditions, but they react badly to swings — a 5-degree temperature drop or a 0.5 pH shift in an afternoon is enough to trigger ich within a week. Build the tank around stability and gentle flow, not around chasing exact target numbers.

Ideal Water Conditions#

Aim for 75-80°F, pH 6.5-7.0, and hardness in the 2-10 dKH range. Soft, slightly acidic water matches their native streams and brings out the best behavior and color. They will tolerate neutral pH (around 7.0-7.2) if it is rock-stable, but anything alkaline or hard above 12 dKH stresses them over time.

Test ammonia and nitrite weekly during the first three months of any new setup, and aim to keep nitrate under 20 ppm with regular water changes. Parameter consistency matters more than hitting an exact number — pick stable, defensible values and hold them.

Tank Size & Schooling Space#

The minimum tank is 30 gallons for a school of 6, and that is a hard floor, not a recommendation. Glass catfish are mid-water swimmers that need horizontal swim room — a tall 29-gallon "column" tank is the wrong shape regardless of total volume. A standard 30-gallon long or 40-gallon breeder gives the school the lateral distance it needs to school naturally.

For a 20-gallon tank, this species is not the right fit. Smaller schools in smaller tanks consistently fail.

Filtration & Flow#

Filtration needs to clean the water without creating strong current. Sponge filters driven by a quiet air pump work well in 30-40 gallon tanks and are the most fish-safe option. Hang-on-back filters work too, but the outflow should be baffled with a pre-filter sponge or directed against the glass to break up the spray bar effect. Canister filters with a spray bar pointed at the back wall also work.

Avoid powerheads, wave makers, and oversized HOB filters. Glass catfish naturally face into a gentle current and will hover in place for hours, but they fatigue quickly in real flow. A tank where every fish gets pushed around when the filter kicks on is too aggressive for this species.

Lighting & Décor#

Subdued lighting brings out the transparency display. Dense planting — Java fern, Amazon sword, hornwort, water sprite — provides cover and breaks up bright overhead light. A dark substrate (black sand, dark gravel, or planted soil capped with sand) makes the fish stand out far more than a bare or light-colored bottom.

Floating plants like frogbit or red root floaters dim the water column further and create the dappled shade these fish prefer. Driftwood and tannins from Indian almond leaves are optional but help replicate the soft, slightly acidic water of the native habitat.

Diet & Feeding#

Glass catfish are carnivores that hunt small invertebrates in the wild. They feed in the mid-water column, take food on the drift, and rarely pick at the substrate. Match those habits and feeding is straightforward. Ignore them and they will simply not eat.

What Glass Catfish Eat#

In captivity, the strongest staples are live or frozen meaty foods: bloodworms, daphnia, brine shrimp (frozen and freshly hatched), tubifex, and chopped mysis. Most individuals will eventually take high-quality micro pellets, slow-sinking carnivore pellets, and quality flake food, but they are slow to convert and may refuse dry food entirely for the first 1-2 weeks after purchase.

Vary the diet across the week — bloodworms two days, brine shrimp two days, pellets the rest. A single-source diet like flake-only leads to slow nutritional decline that you will not notice until the fish thin out and start dying.

Feeding Behavior & Challenges#

Drop food where the school is hovering, not where you wish they were eating. A small clip of frozen bloodworms thawed in tank water and squirted from a pipette directly in front of the school works far better than scattering food at the surface and hoping it drifts to them. Food that hits the substrate is generally lost — they will not go down to find it.

Shy individuals or recently introduced fish often need target feeding with a long pipette or feeding tube for the first few days. Once one fish in the school starts eating prepared food, the rest tend to follow within a week. If after two weeks none of the school is taking dry food, switch to a steady frozen rotation rather than starving them onto pellets.

Tank Mates & Compatibility#

Glass catfish work in peaceful community tanks built around small, slow-to-moderate-paced species. They fail in any tank with aggression, fin nipping, or loud feeding competition.

Ideal Community Partners#

The best mates are small, peaceful, similarly paced fish: ember tetras, neon tetras, harlequin rasboras, chili rasboras, celestial pearl danios, and pygmy or salt-and-pepper corydoras on the bottom. Honey gouramis and dwarf gouramis work as a single, calm centerpiece in a 40-gallon-plus tank. Cherry shrimp can coexist with adult glass catfish in heavily planted tanks, though juvenile shrimp will sometimes get eaten.

A planted community tank with a school of 8 glass catfish, 10-12 small tetras, a small group of corydoras, and one centerpiece is the layout this species shines in.

Schooling Requirement#

Six is the minimum. Eight to ten is better. This is not negotiable — solitary glass catfish stop eating, develop chronic stress, and die. A school of three or four will gradually thin to one or two, then to zero. Stores that bag a single glass catfish for a community tank without warning the buyer about schooling requirements are not doing the species any favors.

Species to Avoid#

• Tiger barbs, serpae tetras, and any other known fin-nippers
• Aggressive cichlids (oscars, jack dempseys, convicts, larger Apistogramma)
• Larger gouramis (especially blue and gold gouramis) that get territorial
• Bettas — generally a poor mix; bettas may nip and they outcompete at feeding time
• Goldfish — wrong temperature range and far too messy
• Anything fast-eating that will hoover up food before the school drifts in to feed

Common Health Issues#

Two issues account for most glass catfish losses: ich triggered by parameter instability, and treatment damage from medications used incorrectly on a thin-skinned, scaleless fish.

Stress-Related Illness#

Ich (white-spot disease) and bacterial fin rot are the two most common diseases, and both are typically triggered by stress: temperature swings, schooling too small, ammonia/nitrite spikes, or harassment from tank mates. The transparency works in your favor here — internal parasites and infections show up earlier on glass catfish than on opaque species. A cloudy patch in the body cavity, visible white worms, or a hollow belly are all reasons to act fast.

Ich Treatment Caution#

Glass catfish are scaleless and thin-skinned, which means they tolerate medications poorly. Use half-dose treatments — half the manufacturer's recommended concentration of any standard ich medication. The safer alternative is heat treatment alone: raise the tank to 86°F for 10-14 days while maintaining strong aeration (warm water holds less oxygen). Combine with daily 25% water changes to reduce parasite load.

Copper Sensitivity#

Avoid all copper-based medications, period. This includes most "general cure" products, marine ich treatments, and any med that lists copper sulfate or chelated copper as an ingredient. Copper kills scaleless fish even at therapeutic doses. Verify ingredients before treating any tank that holds glass catfish.

Breeding Glass Catfish#

Glass catfish are rarely bred in home aquariums. The vast majority of fish in the trade are wild-caught from southern Thailand or commercially farmed in Southeast Asia. Captive home spawning has been reported but is uncommon and not consistently repeatable.

Difficulty & Rarity in Home Aquaria#

Spawning attempts in home tanks generally rely on simulating the rainy-season triggers in the native range: a gradual temperature drop of 4-6°F, soft acidic water, and frequent partial water changes with cooler water. Even with the right cues, success is sporadic and largely undocumented compared to commonly bred species like corydoras or tetras.

Egg Scattering Behavior#

When spawning does occur, glass catfish scatter adhesive eggs among fine-leaved plants like java moss or hornwort. There is no parental care — eggs and fry are at risk from the parents and any tank mates. The fry are extremely small and require infusoria for the first week, then microscopic live foods like vinegar eels or first-stage rotifers. Most attempts fail at the fry-feeding stage. Treat this species as a display fish, not a breeding project.

Where to Buy & What to Look For#

The single biggest factor in long-term success with glass catfish is buying a healthy school from a store that has actually held them long enough to see how they are doing. Freshly imported fish — particularly wild-caught stock that arrived within the last week — have the highest die-off rates regardless of how the buyer cares for them at home.

Signs of a Healthy Fish#

Look for fish that are actively schooling in mid-water, holding position with erect dorsal fins, and showing clear, well-defined organs through the body wall. Cloudiness inside the body, a hollow or pinched belly, clamped fins, or fish drifting alone away from the group are all warning signs.

Their transparency makes a quick visual health check straightforward — most diseases that hide in opaque fish show up early on glass catfish. Take 60 seconds at the tank to actually look at the fish before committing.

Local Fish Store Checklist#

A solid LFS will quarantine new arrivals for at least a week before selling. Ask whether the school in the display tank has been treated for parasites, what they are being fed, and whether the store will hold a deposit on a school of 6+ for a few days while you finish cycling your tank.

If your tank is already cycled and stable, plan to buy the entire school in one visit and acclimate them as a group. Adding glass catfish piecemeal — three this week, three next week — produces more stress than adding all six together.

For a broader overview of community-tank stocking and species selection, see the freshwater fish guide.

Quick Reference#

• Tank size: 30 gallons minimum for a school of 6 (40+ gallons preferred)
• Temperature: 75-80°F
• pH: 6.5-7.0 (soft, slightly acidic)
• Hardness: 2-10 dKH
• School size: 6 minimum, 8-10 ideal
• Diet: Carnivore — frozen bloodworms, daphnia, brine shrimp, micro pellets
• Tank mates: Small peaceful tetras, rasboras, corydoras, honey gourami
• Avoid: Fin nippers, aggressive cichlids, bettas, copper medications
• Lifespan: 7-8 years with stable water
• Difficulty: Intermediate