Blue sheatfish

Where they come from

Blue sheatfish (Kryptopterus cryptopterus) are big, ghosty catfish from Southeast Asia. Think Thailand, Peninsular Malaysia, Sumatra, and Borneo. They cruise the midwater of slow to medium-flowing rivers and flooded forests, usually under shade with loads of tannins and leaf litter. They like dim, calm stretches with plenty of overhanging cover.

Setting up their tank

These guys are midwater schoolers that get big. A small group is a must, and a long tank makes all the difference. They stress easily in bright tanks with no cover, so plan the scape around shade and open lanes to cruise.

• Tank size: 6-foot (120-150 cm) tank as a baseline for a group of 5-7. Think 90-125+ gallons.
• Water: soft to moderately soft, pH 6.0-7.2, temperature 75-82 F (24-28 C).
• Flow and oxygen: steady, not blasting. A canister + a gentle powerhead for circulation works well.
• Lighting: dim. Floaters (salvinia, frogbit) and wood help cut the glare.
• Substrate: sand or smooth fine gravel. Scatter leaves for extra cover and that comfy tea-colored tint.

Aquascape for shade on the sides and an open swimming lane down the middle. I like long driftwood branches pointing forward to break line of sight without chopping up swimming space. Use darker backgrounds and keep reflections down with a black back and side panels if you can.

They hate unstable water. Go for big, regular water changes (30-50% weekly) and keep nitrates low. Drip-acclimate new fish, lights off, and do not rush them into bright or high-flow tanks on day one.

What to feed them

They are carnivorous micro-predators. New arrivals often ignore pellets until they settle, so start with meaty frozen foods and work toward a mixed diet. Smaller, more frequent feedings are better than stuffing them once a day.

• Go-to foods: frozen bloodworms, mysis, chopped prawn, blackworms, daphnia.
• Dry options they learn to take: small sinking carnivore pellets, soft sticks, high-protein granules.
• Feeding rhythm: 2-3 light feedings daily while settling, then 1-2 once they are confident.

How they behave and who they get along with

In groups, they hang like a silky ribbon midwater. Solo or in pairs, they get skittish and go off food. They are peaceful but have decent-sized mouths, so think twice before adding bite-sized tankmates.

• Best kept in a group of at least 5-7.
• Good neighbors: larger rasboras (scissortails), calm rainbowfish of similar size, peaceful larger gouramis, silver dollars, bigger Corydoras or calm loaches that will not harass them.
• Avoid: fin-nippers (tiger barbs), hyper torpedoes (giant danios), aggressive cichlids, and anything small enough to be a snack (tiny tetras, neon rasboras).

Breeding tips

I have not seen a confirmed home-aquarium spawn of K. cryptopterus, and I have asked around. Commercial farms use hormone induction. In the wild they likely cue off seasonal floods and big environmental swings that are hard to copy at home. If you are set on breeding a Kryptopterus, pick the smaller glass catfish species instead.

Common problems to watch for

• Stress from bright light and no cover: leads to hiding, refusal to eat, and sudden dashes. Add floaters and reduce intensity.
• Refusing dry food: start with frozen, feed in current, and blend in small pellets over a week or two.
• Barbel damage on intakes: use prefilter sponges and smooth scaping materials.
• Water-quality sensitivity: they go downhill fast with high nitrate or sudden swings. Keep changes steady and matched for temp and TDS.
• Ich after shipping: they are ich magnets when stressed. Quarantine if you can and treat promptly with heat and an appropriate med.
• Misidentification: stores sometimes sell large Kryptopterus as "glass catfish." If it is not truly transparent and is already 3-4 inches, plan for the bigger tank.