Glass catfish
Kryptopterus vitreolus
intermediate careOverview
The glass catfish (Kryptopterus vitreolus) is one of the aquarium’s true oddities — a genuinely transparent fish whose spine and shimmering internal organs are visible through its clear body. Peaceful and delicate, it hangs in mid-water in loose shoals, drifting at a slight head-up angle. It has a reputation as a difficult fish, but nearly all losses come down to two avoidable mistakes: an unstable tank and too small a group. Get those right and it’s a long-lived, mesmerising species.
Tank & water
A proper shoal needs at least 110 litres (30 gallons) with open mid-water swimming room.
- Stability above all: glass catfish cannot tolerate ammonia, nitrite or big swings. Only add them to a fully cycled, long-settled tank.
- Some flow: they come from flowing waters and appreciate gentle-to-moderate current and oxygenation from the filter.
- Warmth: 23–27 °C held steady with a reliable heater.
- Planting and shade: dense planting and some cover give this timid fish the security it needs to come out and feed.
Feeding
A micropredator, the glass catfish feeds in mid-water and often ignores food that sinks past it. Offer small floating and slow-sinking foods — micro-pellets and flakes from the fish food range — and, crucially, plenty of small live and frozen foods such as daphnia, cyclops, bloodworm and baby brine shrimp, which they take eagerly. Watch that they actually get their share.
Tankmates
Only gentle, peaceful companions: small rasboras and tetras, otocinclus, corydoras, small peaceful gouramis and shrimp. Avoid boisterous, fast or nippy fish that will stress this timid shoaler off its food. Keep a shoal of six or more so they feel secure.
For a calm community around them, browse our best community fish for beginners answer.
Common mistakes to avoid
- Adding them to a new or unstable tank
- Keeping too few — the group is essential
- Boisterous tankmates that stress them
- Food that sinks past them uneaten
Glass catfish — frequently asked questions
Why do glass catfish die so easily?
Almost always because they were added to an immature or unstable tank, or kept in too small a group. Glass catfish are sensitive to poor and swinging water quality and to stress. Add them only to a mature, stable tank, in a shoal of six or more, and they can live for years.
How many glass catfish should I keep?
At least six, and more is better. They are true shoaling fish that hang together in mid-water. Kept alone or in twos and threes they become stressed, stop feeding and waste away — the group is not optional.
Are glass catfish transparent for real?
Yes. Their bodies are genuinely see-through, so you can watch the spine and internal organs. A cloudy or milky appearance is a warning sign of stress or illness — healthy glass catfish are clear.
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