Flying Fox

The Flying Fox is often confused with the Siamese Algae Eater but is a different species with different characteristics. While juveniles eat algae, adults often become less interested in algae and more territorial. They have a distinctive black stripe that does NOT extend through the tail fin, and often show yellowish coloration in the fins. They are more aggressive than true Siamese Algae Eaters and may fight with other algae-eating fish. For actual algae control, Siamese Algae Eaters are superior.

Overview: The Misunderstood Algae Grazer

The Flying Fox represents one of the most commonly misidentified and misunderstood fish in the freshwater aquarium hobby. Named for their sleek, fast-swimming behavior that resembles a flying motion through the water, these fish are frequently confused with their more peaceful and algae-focused cousins, the Siamese Algae Eaters (Crossocheilus species). This confusion has led to countless aquarists purchasing Flying Foxes expecting peaceful, algae-controlling additions to their community tanks, only to discover territorial, increasingly aggressive fish that lose interest in algae as they mature.

Native to the fast-flowing streams and rivers of Southeast Asia, particularly Thailand and the Malay Peninsula, Flying Foxes have evolved for life in high-energy environments. Their streamlined bodies, powerful swimming muscles, and territorial instincts reflect millions of years of evolution in competitive habitats where prime grazing territories represent valuable resources. Understanding these natural behaviors helps explain their aquarium behavior and the challenges they present.

What distinguishes Flying Foxes (Epalzeorhynchos kalopterus) from True Siamese Algae Eaters (Crossocheilus oblongus/reticulatus) extends beyond mere taxonomy. While both fish have dark lateral stripes, careful observation reveals critical differences: the Flying Fox’s stripe stops before the tail fin, while the Siamese Algae Eater’s stripe continues through the tail. Additionally, Flying Foxes often display yellowish-orange coloration in their fins, while Siamese Algae Eaters typically have clear or black fins. These differences, while subtle to the untrained eye, signal dramatically different behaviors and aquarium suitability.

Natural Habitat and Origin

Flying Foxes inhabit fast-flowing freshwater systems across Southeast Asia, with their primary range including Thailand, the Malay Peninsula, and possibly extending into neighboring regions.

Stream and River Environment

In the wild, these fish occupy:

• Fast-flowing streams with rocky substrates
• River sections with moderate to strong currents
• Areas with submerged wood and rocks
• Clear to slightly turbid waters
• Shallow to moderately deep sections (1-10 feet)

Their preference for high-flow environments has shaped their evolution, producing fish that require well-oxygenated water and exhibit territorial behavior around prime feeding locations.

Water Conditions in Nature

Temperature: 74-80°F year-round in tropical regions, with seasonal variations minimal.

pH Levels: 6.0-7.5, varying based on geology and organic matter in specific streams.

Water Hardness: Moderate (3-12 dGH), reflecting dissolved minerals from rocky substrates.

Current: Moderate to strong flow in most habitats, which these fish navigate with powerful swimming.

Oxygenation: Well-oxygenated waters due to flow and turbulence.

The fast-flow, well-oxygenated conditions of their natural habitat explain their need for good water flow and high oxygen levels in aquariums.

Setting Up the Ideal Aquarium

Creating an appropriate environment for Flying Foxes requires attention to space, current, and territory management.

Tank Size and Dimensions

The minimum tank size for a single Flying Fox is 30 gallons, with 40-55 gallons being preferable for long-term success. These active fish require adequate swimming space and territories.

Why Adequate Space Matters:

• Reduces territorial aggression
• Provides room for active swimming behavior
• Allows establishment of grazing territories
• Accommodates appropriate tank mates
• Maintains stable water parameters

A 40-gallon breeder (shallow and wide) provides better territory options than a tall tank of the same volume.

Substrate and Hardscape

Flying Foxes need appropriate surfaces for grazing and territory establishment:

• Smooth gravel or sand: Allows natural grazing
• Driftwood: Essential for grazing and territory markers
• Smooth rocks: Create territories and visual barriers
• Caves: Provide retreats (though they prefer open areas)

Territory Design: Use driftwood and rocks to create distinct zones, allowing the Flying Fox to establish clear territories without viewing the entire tank as its domain.

Water Flow and Filtration

Good water flow is important for Flying Foxes:

• Moderate to strong flow: Simulates natural habitat
• Powerheads: Can supplement filter output
• Position: Create flow patterns without dead zones
• Oxygenation: Good surface agitation for oxygen exchange

Strong filtration helps maintain the water quality these active fish require.

Plant Decorations

While not strictly required, plants provide benefits:

• Security: Reduce stress and aggression
• Water quality: Absorb nitrates
• Visual barriers: Break up sightlines
• Grazing surfaces: Leaves provide additional feeding areas

Choose hardy plants that can withstand the fish’s active swimming. Avoid delicate plants that may be uprooted.

Water Parameters and Maintenance

Flying Foxes are adaptable to various water conditions but have specific preferences.

Temperature Requirements

Maintain temperature between 74-80°F (23-27°C). Use a reliable heater to ensure consistency. These active fish have higher metabolisms and benefit from stable, warm temperatures.

pH and Hardness

Flying Foxes demonstrate good adaptability:

• pH: 6.0-7.5 (wide tolerance range)
• Hardness: Soft to moderate (3-12 dGH)

This flexibility makes them suitable for various community setups, from soft-water planted tanks to moderately hard community aquariums.

Water Quality Maintenance

Perform 25-30% water changes weekly to maintain excellent conditions. Flying Foxes are sensitive to ammonia and nitrite, which must remain at 0 ppm. Keep nitrates below 20 ppm.

Their active nature and feeding habits make them sensitive to water pollution. Consistent maintenance is essential.

Diet and Feeding

Flying Foxes are omnivores with changing dietary preferences as they mature.

Juvenile Diet

Young Flying Foxes are primarily algae grazers:

• Grazing on tank algae
• Algae wafers
• Vegetable matter
• Some protein foods

During this stage, they can help control algae in the aquarium, though less effectively than Siamese Algae Eaters.

Adult Dietary Shift

As Flying Foxes mature (3+ inches), their dietary preferences change:

• Less interest in algae: Adults become less effective algae controllers
• More interest in protein: Will take flake foods, pellets, frozen foods
• Territorial over food: May defend feeding areas
• Competitive eaters: Fast and aggressive at feeding time

Feeding Schedule

Feed 1-2 times daily with a varied diet:

• Algae wafers: Even adults will eat these
• Flake foods: Quality tropical fish flakes
• Vegetables: Blanched zucchini, cucumber
• Frozen foods: Occasional protein treats

Ensure adequate food reaches the bottom for grazing.

Behavior and Temperament

Understanding Flying Fox behavior is essential for successful keeping and appropriate tank mate selection.

Territorial Behavior (Adults)

Adult Flying Foxes establish and defend territories:

• Territory size: Varies based on tank size and competition
• Defense mechanisms: Chasing, flaring fins, ramming
• Target: Primarily other algae-eating fish or similar-looking species
• Timing: Aggression increases as fish mature (4+ inches)

Social Dynamics

• Solitary: Generally prefer to be alone or in pairs with large tanks
• Aggression to similar fish: Fight with other Flying Foxes and Siamese Algae Eaters
• Active swimmers: Constant movement throughout territory
• Fast: Quick, darting movements when disturbed

Juvenile vs. Adult Behavior

Juveniles (under 3 inches):

• More peaceful
• Focused on grazing
• Less territorial
• Better community fish

Adults (4-6 inches):

• Increasingly territorial
• Less interested in algae
• More aggressive
• May bully tank mates

Compatible Tank Mates

Selecting appropriate tank mates requires understanding the Flying Fox’s territorial nature.

Suitable Tank Mates

Fast, Robust Fish:

• Barbs (Tiger, Cherry, Rosy)
• Danios (Zebra, Leopard, Giant)
• Rainbows (Australian, New Guinea)
• Fast Tetras (Serpae, Black Skirt)
• Larger Rasboras

Other Bottom Dwellers:

• Corydoras Catfish (larger species)
• Loaches (Clown, Yoyo - with caution)
• Plecos (Bristlenose, larger species)

Upper Level Fish:

• Gouramis (larger, robust species)
• Larger Tetras
• Peaceful Cichlids (Keyhole, some Geophagus)

Incompatible Tank Mates

Never House With:

• Siamese Algae Eaters: Will fight to establish dominance
• Other Flying Foxes: Territorial warfare
• Chinese Algae Eaters: Direct competition and aggression
• Slow, peaceful fish: Will be bullied
• Long-finned fish: May have fins nipped
• Other Epalzeorhynchos species: Similar appearance triggers aggression
• Small, delicate fish: Outcompeted for food, possibly bullied

Identification: Flying Fox vs. Siamese Algae Eater

Proper identification is crucial for appropriate care and expectations.

Flying Fox (Epalzeorhynchos kalopterus)

• Stripe: Black lateral stripe STOPS before tail fin
• Fins: Yellowish-orange coloration, especially in dorsal and caudal fins
• Body: Slightly deeper body
• Mouth: More pronounced
• Behavior: Territorial, less effective algae control as adult
• Algae preference: Less dedicated algae eater

True Siamese Algae Eater (Crossocheilus oblongus or C. reticulatus)

• Stripe: Black lateral stripe continues THROUGH tail fin
• Fins: Clear or black, no yellow/orange
• Body: More streamlined
• Mouth: Less pronounced
• Behavior: Peaceful, consistent algae control throughout life
• Algae preference: Dedicated algae eater, including black beard algae

Critical Difference: The stripe ending vs. continuing through the tail is the most reliable identification method.

Recommendations for Aquarists

For Algae Control

If your primary goal is algae control, choose Siamese Algae Eaters instead of Flying Foxes. SAEs:

• Remain peaceful throughout life
• Continue eating algae as adults
• Are more effective at controlling various algae types
• Can be kept in groups
• Do not develop territorial aggression

For Community Tanks

Flying Foxes can work in community tanks if:

• Kept singly (one per tank)
• Housed with fast, robust tank mates
• Provided adequate space (40+ gallons)
• Monitored for developing aggression
• Removed if they become problematic

Species Tank Option

A single Flying Fox in a 30-40 gallon tank with fast, compatible fish can be a suitable setup. This eliminates competition with other algae-eating fish.

Common Health Issues and Prevention

Flying Foxes are generally hardy but can suffer from common freshwater fish ailments.

Ich (White Spot Disease)

Symptoms: White spots, flashing, rapid breathing.

Treatment: Heat to 86°F with medication. They tolerate heat well.

Fin Damage

Cause: Territorial fighting or aggressive tank mates

Symptoms: Torn or damaged fins

Prevention: Avoid keeping with other territorial fish or similar species

Starvation (Adults)

Cause: Competing with faster fish, inadequate plant matter

Symptoms: Thin, lethargic

Prevention: Ensure adequate food reaches them; target feeding

Tips for Success

• Verify identification: Make sure you have a Flying Fox, not a Siamese Algae Eater
• One per tank: Never keep multiple Flying Foxes or with SAEs
• Plan for aggression: Adults become territorial—prepare accordingly
• Don’t rely on algae control: Adults lose interest; have alternative plans
• Choose tank mates carefully: Fast, robust fish only
• Provide driftwood: Essential for grazing and territory establishment
• Maintain good flow: Simulates natural habitat
• Monitor as they grow: Be prepared to relocate if aggression becomes problematic
• Feed varied diet: Don’t rely solely on algae
• Large tank preferred: 40+ gallons reduces territorial behavior
• Have backup plans: Be ready to rehome if they don’t work in your setup
• Buy juveniles: Less aggressive, better algae control
• Observe daily: Watch for signs of bullying or stress in tank mates
• Realistic expectations: Understand they are not SAE replacements

Frequently Asked Questions (FAQ)

What’s the difference between a Flying Fox and a Siamese Algae Eater?

The most reliable difference is the black stripe: Flying Fox stripe STOPS before the tail, while SAE stripe goes THROUGH the tail. Flying Foxes also often have yellowish fins.

Do Flying Foxes eat algae?

Juveniles eat algae, but adults often lose interest and become less effective. They are inferior to Siamese Algae Eaters for algae control.

Are Flying Foxes aggressive?

Adults can be semi-aggressive and territorial, especially toward similar-looking fish like Siamese Algae Eaters. Juveniles are more peaceful.

Can I keep two Flying Foxes together?

Generally not recommended. They are territorial and will fight. One per tank is the safest approach.

Can I keep a Flying Fox with a Siamese Algae Eater?

No. They will likely fight. These combinations usually end badly for one or both fish.

How big do Flying Foxes get?

They reach 4-6 inches (10-15 cm) in length. Their size contributes to their territorial behavior.

What size tank do they need?

Minimum 30 gallons, with 40+ gallons being better for managing their territorial behavior.

Are they good algae eaters?

Not particularly, especially as adults. If algae control is your primary goal, choose Siamese Algae Eaters instead.

What should I feed Flying Foxes?

Algae wafers, quality flakes, blanched vegetables, and occasional frozen foods. Don’t rely solely on tank algae.

How long do Flying Foxes live?

6-10 years with proper care. Long lifespan means long-term commitment to managing their behavior.

Why is my Flying Fox chasing other fish?

Territorial behavior, especially as they mature. May also be competing with other algae-eating fish or defending food sources.

Can Flying Foxes live with shrimp?

Small shrimp may be eaten. Larger shrimp might survive but could be harassed.

Do they need a heater?

Yes, they are tropical fish requiring 74-80°F stable temperatures.

Are they good for beginners?

Beginner level regarding care, but their territorial behavior requires planning. Beginners may be better served by Siamese Algae Eaters.

Can I keep a Flying Fox in a planted tank?

Yes, they work well in planted tanks and won’t damage plants. Plants provide grazing surfaces and visual barriers.

Do they jump?

They can jump when startled. A lid is recommended, though less critical than for some other species.

What temperature do they prefer?

74-80°F (23-27°C), with 76-78°F being ideal for most aquariums.

Can they live with cichlids?

Sometimes, with peaceful, larger cichlids. Avoid aggressive cichlids. Monitor closely for compatibility.

Do Flying Foxes need driftwood?

While not strictly required, driftwood provides grazing surfaces and helps establish territories. Recommended.

Why did my Flying Fox stop eating algae?

Adult Flying Foxes often lose interest in algae as their diet shifts toward other foods and they become more territorial. This is normal behavior.

Conclusion

Flying Foxes represent a case study in the importance of proper fish identification and understanding species-specific behaviors. While they are attractive, active fish that can add interest to community aquariums, their reputation has suffered from widespread confusion with the more peaceful and algae-focused Siamese Algae Eater.

Success with Flying Foxes requires realistic expectations: they are not algae-control specialists, especially as adults, and they develop territorial behaviors that demand careful tank planning. When kept singly with fast, robust tank mates in adequately sized aquariums, they can be interesting long-term inhabitants. However, aquarists seeking primarily algae control should choose Siamese Algae Eaters instead.

The key to Flying Fox success lies in understanding what they are—and what they are not. They are active, territorial fish that transition from algae-grazing juveniles to omnivorous, territorial adults. They are not peaceful community fish that can be kept in groups, nor are they solution for persistent algae problems. Give them adequate space, appropriate tank mates, and realistic expectations, and these swift swimmers from Southeast Asian streams can become engaging aquarium residents for years to come.