Flying Fox (Epalzeorhynchos kalopterus)

Territorial aggression is hardwired Flying Fox behavior, not a personality flaw. Understanding the triggers allows you to manage it effectively.

Primary Aggression Triggers

• Conspecifics: Two Flying Foxes in the same tank will fight. This is non-negotiable biology.
• Similar-looking fish: Red Tail Sharks, Rainbow Sharks, and even some loaches trigger territorial responses because the Flying Fox perceives them as competitors for the same bottom-dwelling niche.
• Insufficient territory: Without defined caves, driftwood structures, and plant barriers, the fish claims the entire bottom as its domain.
• Tank size: Tanks under 30 gallons amplify aggression because escape routes are limited.

Mitigation Strategies

• House only one Flying Fox per tank.
• Avoid all shark-like bottom dwellers (Red Tail Shark, Rainbow Shark, similar Epalzeorhynchos species).
• Provide at least three distinct cave or tunnel structures using driftwood or smooth rocks.
• Use dense planting along the back and sides to create visual barriers.
• Ensure the tank footprint is at least 36 inches (90 cm) long to allow chased fish to escape the territory.
• Feed adequately at multiple locations to reduce resource competition.

If aggression persists after these modifications, the fish may simply be incompatible with your chosen community. Some individuals are more territorial than others.

Tank mate selection for Flying Foxes follows one rule: avoid anything that looks like a competitor for the bottom territory or anything small enough to be harassed into stress.

Compatible Tank Mates

• Mid-water schooling fish: Tiger Barbs, Rosy Barbs, Cherry Barbs, Odessa Barbs, and Danios. These occupy a different water layer and are fast enough to avoid territorial disputes.
• Upper-water fish: Gouramis (Pearl, Blue, Gold), Angelfish, and larger Tetras (Congo, Bleeding Heart, Emperor). These avoid the Flying Fox's territory entirely.
• Peaceful bottom dwellers: Corydoras catfish (in groups of 6+), larger loaches (Clown Loach, Yoyo Loach), and peaceful plecos (Bristlenose, Rubberlip).
• Larger community fish: Swordtails, Mollies, and Platies in appropriately sized tanks.

Species to Avoid

• Other bottom-dwelling sharks: Red Tail Shark (Epalzeorhynchos bicolor), Rainbow Shark (Epalzeorhynchos frenatum), and any other Epalzeorhynchos species. Fatal territorial warfare is guaranteed.
• Other Flying Foxes: Conspecific aggression is severe and chronic.
• Long-finned, slow fish: Betta fish, fancy Guppies, and Veiltail Angelfish will have their fins nipped.
• Very small fish: Neon Tetras, Cardinal Tetras, and Ember Tetras may be stressed into hiding by persistent chasing, even if not physically eaten.
• Slow, docile bottom dwellers: Kuhli Loaches and small Corydoras species may be bullied away from food.

Breeding Flying Foxes in home aquariums is extremely rare and not recommended for hobbyists. These fish require specific environmental triggers and substantial space that exceed typical home aquarium capabilities.

Commercial breeding involves conditioning a group of 5 to 6 sexually mature adults (3+ inches or 7.5+ cm) with high-protein foods including bloodworms and brine shrimp for 4 weeks. Spawning is triggered by simulating the monsoon season: lowering water temperature to 68°F (20°C), performing a 50% water change with cool reverse-osmosis water over 6 hours, and increasing water flow to mimic rainfall runoff.

Flying Foxes are egg-scatterers. Females release 500 to 1,000 adhesive eggs among spawning mops or Java moss. Parents must be removed immediately after spawning to prevent egg consumption. Eggs hatch in 24 to 36 hours at 75°F (24°C). Fry require green water (infusoria) for the first 5 days, transitioning to baby brine shrimp and microworms thereafter.

The logistical demands, space requirements, and low success rate make captive breeding an endeavor for dedicated breeding facilities rather than home aquarists. Focus your efforts on providing exemplary long-term care for a single specimen.

Flying Foxes are generally hardy when maintained in proper water conditions, but they are susceptible to the standard cyprinid disease suite. Early detection and correct medication selection are critical because their scale structure limits certain treatments.

Fin Rot

Caused by Aeromonas, Pseudomonas, or Vibrio bacteria, fin rot manifests as ragged, receding fins with white or red edges. It is almost always triggered by poor water quality, overcrowding, or fin-nipping from tank mates. Treatment requires simultaneous water quality correction (25% daily water changes, gravel vacuuming) and antibiotic therapy. Use erythromycin (Maracyn) or a broad-spectrum gram-negative antibiotic. Remove activated carbon during treatment. Complete the full course even if fins appear healed.

Ich (White Spot Disease)

Ichthyophthirius multifiliis presents as white salt-like spots across the body and fins, accompanied by flashing against decor. Raise temperature to 86°F (30°C) for 10 to 14 days if tank mates tolerate it, combined with formalin-free ich treatment at half-dose due to cyprinid sensitivity. Alternatively, use copper-based treatments at 0.2 mg/L, which Flying Foxes tolerate well.

Internal Parasites

Wild-caught specimens or fish fed live foods may carry nematodes or tapeworms. Symptoms include weight loss despite normal feeding and stringy white feces. Treat with praziquantel at standard dose, which is safe for this species.

Fungal Infections

Cotton-like growths on fins or body, typically secondary to physical injury or fin rot. Treat with methylene blue baths or malachite green at half-standard dose (0.05 mg/L) to avoid toxicity.

Prevention remains the best medicine: maintain nitrates below 20 ppm, perform weekly water changes, quarantine new fish for 2 weeks, and avoid overfeeding.