Goldstriped flying fox

Where they come from

Goldstriped flying fox (Crossocheilus cobitis) show up in fast-ish freshwater systems in Southeast Asia - think warm rivers and streams with current, rocks, and lots of biofilm to graze. They are built to cruise, cling, and pick at surfaces all day.

If you have kept the more common Siamese algae eater (Crossocheilus oblongus), this one feels like its more intense cousin. Similar shape and habits, but it demands more space and better tank management, especially as it grows.

Setting up their tank

Give them room first. These are active, muscular fish that spend the whole day patrolling, and they get pushy in tight quarters. A long tank beats a tall one every time.

• Tank size: I would not do them in anything under a 4-foot tank. Bigger is noticeably easier.
• Flow and oxygen: moderate to strong current plus good surface agitation. They act stressed in stale water.
• Filtration: overfilter. They are constant grazers and poopers, and they do better with very clean water.
• Scape: smooth rocks, driftwood, and lots of hard surfaces for algae/biofilm. Leave open lanes for swimming.
• Plants: tougher plants (anubias, java fern, bolbitis) attached to wood/rock do better than delicate stems in a high-flow setup.
• Lid: they can spook and jump, especially right after you add them. Cover gaps.

Water numbers are less magic-number and more stability. Neutral-ish pH, warm tropical temps, and low nitrogen waste is the game. What they hate is swings, dirty substrate, and oxygen-poor water.

What to feed them

They will graze algae and aufwuchs, but you cannot run them as "the algae solution" and call it a day. In a clean aquarium, natural growth usually is not enough.

• Daily staple: good algae wafers or spirulina-based pellets
• Veg rotation: blanched zucchini, cucumber, green beans, spinach (clip it down so it does not float and rot)
• Protein a few times a week: frozen bloodworms, brine shrimp, daphnia, or a quality sinking community pellet
• Grazing help: leave some rocks in brighter areas to grow a film, or rotate a couple of "algae rocks" between tanks/buckets under a light

Watch the belly. A healthy flying fox has a gently rounded underside, not hollow. If it is getting skinny, increase feeding frequency and add more sinking foods that reach the bottom quickly.

How they behave and who they get along with

Juveniles can be pretty chill, then they hit a size where they decide they own the floor plan. They are not usually "murder fish," but they can turn into relentless chasers, especially toward similar-shaped algae eaters.

• Temperament: active, sometimes bossy; can become territorial with age
• Best group size: one is simplest. Groups can work in very large tanks with lots of line-of-sight breaks, but expect a pecking order.
• Tankmates that usually work: larger barbs, danios, rasboras, rainbowfish, sturdy tetras, many loaches (in a big tank)
• Tankmates I avoid: other Crossocheilus, SAE/"flying fox" lookalikes, Chinese algae eaters, timid bottom fish, long-finned slow fish (they may pester)

They spend most of their time on rocks, wood, glass, and the substrate, but they also do quick midwater sprints. If they are glass-surfing constantly, darting, or hiding all day, check flow, oxygen, and ammonia/nitrite first.

Breeding tips

Breeding Crossocheilus cobitis in home aquariums is not something you should count on. Most of what you see in shops is wild-caught or produced in commercial setups, often with hormone assistance.

If you want to play the long game, the best you can do is keep a healthy group in a big, river-style tank, feed heavily with a mix of greens and protein, and keep water changes consistent. Even then, expect zero eggs and be pleasantly surprised if you ever see spawning behavior.

Common problems to watch for

• Starvation in a "too clean" tank: they look fine for weeks, then suddenly get thin. Supplement greens and sinking foods from day one.
• Ich and stress outbreaks after purchase: they ship poorly sometimes. Quarantine helps a lot.
• Bloat/constipation: too much rich food and not enough roughage. Add more veg and algae-based foods, and do not overdo bloodworms.
• Aggression ramping up with age: sudden chasing and fin nipping, especially in smaller tanks or with similar fish.
• Oxygen issues: hanging near the surface or acting sluggish in warm water usually means add aeration/flow now, not later.
• Misidentification: many fish sold as "flying fox" are actually Chinese algae eaters or other lookalikes that behave differently.

Big water changes and clean substrate go a long way with this species. They are tough once settled, but they do not forgive neglected maintenance the way some hardier community fish do.