Quick Answer
Flying Fox fish (Epalzeorhynchos kalopterus) are territorial algae grazers that must be kept singly. They need at least 100 gallons, strong water flow, and will bully bottom-dwellers. Most fish sold as “Flying Foxes” are actually Siamese Algae Eaters — know the difference before you buy.
You bought a “Flying Fox” to clean up algae. Six months later, it’s terrorizing your corydoras and hasn’t touched the black beard algae taking over your driftwood. Sound familiar?
Here’s the problem: most aquarists don’t actually have a Flying Fox. They have a Siamese Algae Eater that was mislabeled at the store. And even when you do get the real thing, this fish comes with behavioral baggage that generic care guides gloss over.
Flying Fox at a Glance
Quick Care Overview
Scientific Name: Epalzeorhynchos kalopterus
Adult Size: Up to 6 inches
Minimum Tank: 100 gallons
Lifespan: 8+ years
Temperature: 68-79°F
pH: 6.0-7.5
Hardness: 5-12 dGH
Temperament: Territorial, aggressive to conspecifics
Social: Keep singly only
Diet: Omnivore (algae, biofilm, meaty foods)
The Identification Problem Nobody Warns You About
This is the single most important section of this care guide, and most articles bury it at the bottom.
Three fish get sold as “Flying Fox” in stores. Only one actually is. The care requirements overlap, but the behavioral differences matter — especially if you’re buying this fish specifically for algae control.
| Species | Black Stripe | Mouth Flaps | Eats BBA? | Aggression |
|---|---|---|---|---|
| True Flying Fox E. kalopterus |
Smooth edges, ends at tail base | Yes — small barbel-like flaps | Rarely | High to own species + bottom dwellers |
| Siamese Algae Eater Crossocheilus oblongus |
Ragged edges, extends into tail fin | No | Yes — one of few fish that will | Moderate, calms with age |
| Siamese Flying Fox Epalzeorhynchos sp. |
Tapers thinner toward tail | Yes | Sometimes | Very high |
| False Flying Fox Garra cambodgiensis |
No black stripe | Modified disc-shaped mouth | Green algae only, not red | Extremely territorial |
[WARNING] Before You Buy
If you’re buying specifically for black beard algae control, you probably want a true Siamese Algae Eater (Crossocheilus oblongus), not a Flying Fox. The Flying Fox largely ignores BBA and becomes increasingly territorial as it matures. This is the single most common mismatch between what people want and what they actually get.
The practical identification challenge: these fish don’t hold still. Looking for mouth flaps on a darting 3-inch juvenile in a store tank is nearly impossible. Your best bet is the stripe pattern — check if it extends into the tail fin (SAE) or stops at the tail base (Flying Fox).
Natural Habitat and What It Tells You
Flying Foxes come from flowing rivers and streams across Southeast Asia — Thailand, Malaysia, Sumatra, Java, and Borneo. During the wet season, they migrate into flooded forest areas.
This origin explains why they need strong flow and high oxygenation. It also explains why they do poorly in stagnant, overstocked tanks — conditions completely foreign to their evolutionary background.
Wild fish graze biofilm and algae off rocks and sandy substrates. They also take small crustaceans and insect larvae — they’re omnivores, not strict herbivores.
Tank Setup
Size Requirements
100 gallons minimum. This isn’t negotiable.
Yes, they only grow to 6 inches. But these fish are active swimmers that patrol large territories. In smaller tanks, their territorial aggression compounds — they can’t establish a territory large enough to feel secure, so they harass everything constantly.
The “one inch per gallon” rule doesn’t apply here. Think in terms of horizontal swimming space and territorial footprint, not simple bioload math.
Water Parameters
- Temperature: 68-79°F (20-26°C)
- pH: 6.0-7.5
- Hardness: 5-12 dGH
- Flow: Moderate to strong — they come from rivers, not ponds
[FACT] Flying Foxes are intolerant of organic waste accumulation. In tanks with poor maintenance, they’re often the first fish to show stress. Weekly 25% water changes aren’t optional — they’re baseline.
Aquascaping
Replicate a riverine environment:
- Sandy or fine gravel substrate with larger water-worn stones
- Driftwood and roots for grazing surfaces and territorial boundaries
- Live plants — they won’t eat healthy plants, and the biofilm on leaves provides natural grazing
- Bright lighting to encourage some algae growth on hardscape
The aquascaping serves a behavioral function beyond aesthetics. Line-of-sight breaks reduce aggression. Defined territories (a particular driftwood piece, a rock formation) give the fish something to claim and defend without harassing tankmates constantly.
Diet
Flying Foxes are omnivores that graze continuously. They’ll eat some algae, but don’t expect them to be your cleanup crew — they have preferences and will ignore types they don’t like.
What they’ll eat:
- Green algae and biofilm on hardscape
- High-quality algae wafers
- Blanched vegetables — zucchini, cucumber, spinach, shelled peas
- Frozen foods — bloodworms, brine shrimp, daphnia
- Quality flakes and sinking pellets
What they won’t reliably eat:
- Black beard algae (despite what some sources claim)
- Hair algae in significant amounts
[TIP] Pro Tip
Feed after lights-out occasionally. Flying Foxes are most active at dawn and dusk in the wild, and some individuals feed more readily when lighting is subdued. This also lets them eat without having to compete with more aggressive midwater feeders.
The Aggression Problem
This is where most care guides fail you. They mention “can be territorial” and move on. Let me be direct: mature Flying Foxes are frequently aggressive enough to kill.
What happens:
- Juveniles under 3 inches are relatively peaceful
- As they mature, they establish territories
- They attack fish that enter their territory — relentlessly
- Bottom-dwellers (corydoras, plecos, loaches) bear the worst of it because they can’t escape to upper water
- Keeping multiple Flying Foxes leads to constant fighting, sometimes to the death
Good tankmates:
- Robust midwater swimmers — barbs, larger tetras, rainbowfish
- Surface dwellers — hatchetfish, some killifish
- Fish fast enough to evade harassment
Avoid:
- Other Flying Foxes (one per tank, period)
- Bottom-dwelling catfish, especially peaceful species like corydoras
- Slow-moving or shy fish that can’t escape
- Other Epalzeorhynchos species (Rainbow Sharks, Red-Tailed Black Sharks) — territory wars
Did You Know?
Flying Foxes become more territorial with age, not less. The relatively peaceful juvenile you bought will likely become increasingly aggressive over its 8+ year lifespan. Plan for the adult behavior, not the baby you see at the store.
Breeding
There are no documented cases of hobbyist breeding for E. kalopterus. The fish sold commercially are either wild-caught or bred using hormone induction at commercial facilities. Don’t plan on breeding these at home.
Should You Get One?
The Flying Fox is a beautiful, long-lived fish with a striking appearance. It’s also demanding in terms of space, potentially aggressive, and frequently misidentified.
Get a Flying Fox if:
- You have 100+ gallons with robust midwater fish
- You want ONE, not multiple
- You’re not counting on it for serious algae control
- You’re prepared for increasing territorial behavior as it matures
Skip it if:
- You keep peaceful bottom-dwellers you want to protect
- You specifically need black beard algae eaten (get a true SAE instead)
- Your tank is under 100 gallons
- You want a group of the same species
Frequently Asked Questions
Do Flying Fox fish eat black beard algae?
Rarely, and not reliably. Despite their reputation as algae eaters, Flying Foxes largely ignore black beard algae. If BBA is your problem, you want a true Siamese Algae Eater (Crossocheilus oblongus), which is one of the few fish that actually consumes it.
Can you keep multiple Flying Fox fish together?
No. Flying Foxes are highly territorial toward their own species and will fight, sometimes fatally. Keep only one per tank, regardless of tank size. This isn’t a case where “more space” solves the problem — their conspecific aggression is hardwired.
How do you tell a Flying Fox from a Siamese Algae Eater?
Check the black lateral stripe. On a true Flying Fox, the stripe has smooth edges and stops where the tail fin begins. On a Siamese Algae Eater, the stripe has rougher, more ragged edges and extends into the tail fin itself. Flying Foxes also have small barbel-like flaps at the corners of their mouths, though these are hard to see on active fish.
Will Flying Fox fish eat shrimp?
Adult shrimp (Amano-sized and larger) are generally safe. However, baby shrimp and small dwarf shrimp species may be eaten. Flying Foxes are omnivores that eat small crustaceans in the wild, so assume shrimplets are at risk.
Why is my Flying Fox chasing other fish?
This is normal mature behavior, not a sign of illness or stress. Flying Foxes become increasingly territorial as they age, especially toward bottom-dwelling fish that enter their claimed territory. Adding more line-of-sight breaks (plants, driftwood, rocks) can reduce harassment, but won’t eliminate it. If the aggression is severe, the targeted fish may need to be rehomed.
Flying Foxes can work beautifully in the right tank — but that tank needs to be large, stocked appropriately, and maintained by someone who understands what they’re signing up for. [INTERNAL LINK: “Siamese Algae Eater care” -> siamese-algae-eater] if BBA control is your actual goal, or [INTERNAL LINK: “best algae eaters” -> algae-eater] for a full comparison of your options.
