The Flying Fox is an elegant bottom-dwelling fish from Southeast Asia, highly prized for its algae-eating habits and striking striped coloration.
Overview
The Flying Fox (Epalzeorhynchos kalopterus) is a freshwater fish from the Cyprinidae family, native to fast-flowing rivers and streams of Southeast Asia, primarily found on the islands of Borneo, Sumatra, and in Thailand. In the wild, it inhabits areas with rocky substrates, moderate to strong currents, and lush vegetation along the banks.
This fish reaches 12-15 cm in length and lives for 5 to 8 years with proper care. The body of Epalzeorhynchos kalopterus is elongated and streamlined, perfectly adapted for life in flowing water. Its most distinctive feature is a broad black horizontal stripe running from the tip of the snout to the base of the caudal fin, bordered above by a bright golden-yellow line. The back is olive-brown while the belly is pale. The fins carry a reddish hue with dark edges, giving the fish an ornate appearance.
The Flying Fox is often purchased specifically for its ability to consume algae, including filamentous types and growths on decorations. However, it is important to understand that Epalzeorhynchos kalopterus is less effective at algae control compared to the Siamese Algae Eater (Crossocheilus oblongus), and with age increasingly prefers prepared foods. It is also frequently confused with the Siamese Crossocheilus — the key difference is that the Flying Fox has smoother edges on its black stripe and reddish-tinted fins.
Tank Requirements
The Flying Fox requires an aquarium of at least 120 liters. Optimal water parameters are: temperature 24-28°C, pH 6.0-7.5, and general hardness (GH) 5-12 dGH. This fish prefers clean, well-oxygenated water with moderate to strong flow that mimics the conditions of its natural habitat.
The substrate should consist of fine gravel or coarse sand to replicate the rocky bottoms of mountain streams. The tank should be furnished with natural driftwood and rocks forming shelters and small caves. The Flying Fox spends a significant amount of time near the bottom and among decorations, so providing numerous hiding spots is essential. Live plants are welcome, though the fish may nibble on soft-leaved species.
A tight-fitting lid is mandatory — Epalzeorhynchos kalopterus is capable of jumping out of the water, especially during stressful situations or when acclimating to a new tank. Moderate lighting is preferred, which also encourages the growth of algae — a natural food source for this fish.
Feeding and Diet
In the wild, Epalzeorhynchos kalopterus is an omnivorous fish with a strong herbivorous tendency. It feeds on algal growth, periphyton, small invertebrates, and detritus. In the aquarium, it is important to provide a varied diet based on plant-based foods.
The staple diet should consist of spirulina tablets and vegetable-based sinking pellets. Be sure to supplement with blanched vegetables: zucchini, cucumber, and spinach leaves. As a protein supplement, offer live or frozen foods two to three times a week — bloodworms, brine shrimp, and daphnia. This will maintain the fish's health and vibrant coloration.
Feed once or twice daily in small portions, preferably in the evening when the fish is most active near the bottom. Do not rely on the Flying Fox feeding exclusively on algae — with insufficient feeding, the fish may begin to damage delicate aquarium plants.
Care and Maintenance
The Flying Fox has a moderate care level (3 out of 5), making it suitable for aquarists with some experience. The foundation of care is maintaining stable water parameters and performing regular water changes (20-30% of volume weekly). Sudden changes in temperature or water chemistry are poorly tolerated by this species.
Effective filtration is essential — an external canister filter is recommended to create adequate flow while providing mechanical and biological filtration. Test ammonia, nitrite, and nitrate levels weekly. Nitrate concentrations should not exceed 20 mg/L.
Regularly inspect the fish for external signs of disease — faded coloration, frayed fins, or spots on the body. Epalzeorhynchos kalopterus is reasonably hardy, but deteriorating water quality can make it susceptible to bacterial and fungal infections. Early detection of problems significantly improves the chances of successful treatment.
Compatibility
The Flying Fox has a moderate aggression level (3 out of 5). While peaceful in its youth, it may display territorial behavior as it matures, particularly toward fish with a similar body shape and coloration. Keeping multiple Flying Foxes in the same tank is only advisable in larger setups (200 liters or more) with abundant hiding places.
Good tank mates include active, peaceful fish of medium size: Tiger Barbs, Harlequin Rasboras, Congo Tetras, and Corydoras. These species are sufficiently active and do not compete with the Flying Fox for territory.
It is not recommended to keep Epalzeorhynchos kalopterus with Red-Tailed Black Sharks, Chinese Algae Eaters, or Siamese Algae Eaters — all of these species occupy a similar ecological niche, which inevitably leads to conflict. Slow-moving and long-finned fish such as angelfish and bettas should also be avoided, as the Flying Fox may chase them and nip their fins.
Breeding
Breeding Epalzeorhynchos kalopterus in home aquariums is considered a difficult task (level 4 out of 5). To date, successful spawning events in amateur aquariums are extremely rare, and the vast majority of specimens available in the trade are wild-caught or produced on commercial farms using hormonal stimulation.
Sexual dimorphism is minimal — females are generally slightly fuller than males, especially when approaching spawning readiness. For a breeding attempt, a spacious spawning tank (150 liters or more) with soft, slightly acidic water (pH 6.0-6.5, GH 3-6) is required. The temperature should be gradually raised to 27-28°C while simultaneously increasing water change frequency to simulate the rainy season.
Fine-leaved plants or artificial spawning mops can serve as spawning substrate. After spawning, the adults must be removed immediately, as they are prone to eating their own eggs. Fry emerge after 24-48 hours and begin free-swimming by day 3-4. Initial foods include infusoria and brine shrimp nauplii. Given the low probability of success, breeding the Flying Fox is recommended only for experienced aquarists prepared for meticulous work.