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Swordtail Tetra: A Comprehensive Guide (Corynopoma riisei)

The Swordtail Tetra (Corynopoma riisei) is one of the most unique and personality-packed fish you can add to a freshwater aquarium. At first glance, it looks like a fairly simple silver tetra—but once you notice the male’s extended tail “sword” and bizarre head structures, you realize this fish is on a completely different level.

This species isn’t just about looks either—it’s known for one of the strangest and most fascinating courtship displays in the hobby. Males actively “present” themselves to females using specialized organs near their gills, making them one of the most behaviorally interesting characins you can keep.

They’re not super common, but for hobbyists who like fish with personality and behavior, this one is a hidden gem.

Natural Distribution & Habitat

Corynopoma riisei comes from northern South America, including:

  • Venezuela
  • Colombia
  • Trinidad and nearby regions

They’re found in:

  • Slow-moving streams
  • Floodplain habitats
  • Shallow, vegetation-rich waters

Typical conditions include:

  • Warm temperatures
  • Slightly acidic to neutral water
  • Moderate plant cover
  • Calm or gently flowing water

They spend most of their time in the upper to midwater, often near the surface.

Size

Swordtail Tetras stay fairly small.

  • Adult size: 2–2.5 inches

However, males appear larger due to:

  • Extended tail filament (“sword”)
  • More developed finnage

Aquarium Care

These are easy, adaptable fish, but they do best in setups that give them space to move and display.

  • Tank size: 20 gallons minimum (30+ preferred)
  • Aquascape: Plants around the edges, open swimming space in the middle
  • Substrate: Sand or fine gravel
  • Lighting: Moderate

Important note:

👉 They are surface-oriented and can jump
👉 A tight-fitting lid is highly recommended

They look best in slightly calmer setups rather than high-flow tanks.

Water Parameters

They’re pretty forgiving.

  • Temperature: 74–80°F
  • pH: 6.0–7.5
  • Hardness: Soft to moderate

As long as the water is stable and clean, they do well.

Diet

No issues here—they’re not picky.

They’ll take:

  • Flake
  • Small pellets
  • Frozen foods (brine shrimp, daphnia)
  • Live foods (great for conditioning)

If you feed them well, you’ll see better:

  • Color
  • Activity
  • Display behavior

Behavior & Tank Mates

Swordtail Tetras are:

  • Peaceful
  • Active
  • Slightly quirky

They do best in:

  • Groups of 6–10+

Tank mates:

  • Other peaceful tetras
  • Rasboras
  • Corydoras
  • Dwarf cichlids

They hang mostly in the upper and middle water column.

One thing to note:

👉 Males can be persistent when displaying to females
👉 Not aggressive—just… enthusiastic

The Wild Part: Their Courtship Behavior

This is what makes Corynopoma riisei special.

Males have:

  • Modified gill structures called gill glands
  • A tail extension used for display

During courtship, the male will:

  1. Position himself near the female
  2. Flick and display his tail
  3. Release pheromones from the gill gland
  4. Try to guide the female into spawning position

It’s honestly one of the more interactive and visible mating displays you’ll see in a tetra.

It feels way closer to cichlid-level behavior than typical characins.

Breeding

They are egg scatterers, but with a twist due to their courtship.

  • Eggs are released in open water or near plants
  • No parental care
  • Eggs hatch in a few days

If you want to breed them:

  • Use fine plants or spawning mops
  • Remove adults after spawning
  • Feed fry very small foods initially

Fun Facts & Hobby Notes

The “sword” isn’t just for looks.
It’s part of the male’s display and plays a role in courtship.

They use chemical signaling.
That gill gland actually releases pheromones—pretty rare to see so clearly in aquarium fish.

They’re more interactive than most tetras.
You’ll actually watch behavior, not just movement.

They’re a conversation fish.
Anyone who notices them is going to ask what they are.

Why Aquarists Love Them

This is one of those species that flies under the radar—but shouldn’t.

Why they’re awesome:

  • Unique tail and body shape
  • Wild courtship behavior
  • Easy to care for
  • Great in community tanks
  • Something completely different from standard tetras

If you’re bored of the usual tetra lineup and want something with real personality, this is it.

Looking to Add Fish to Your Aquarium?

If you're looking to add new fish to your aquarium, we recommend purchasing from trusted retailers known for their healthy livestock and excellent selection. The Wet Spot Tropical Fish has one of the best selections of rare and high-quality freshwater fish in the hobby, with excellent shipping and consistently healthy stock. Moonlight Aquatics is another fantastic source, especially for uncommon species and great prices on unique fish you don’t see everywhere. If you’re looking to add shrimp to your tanks, Buy Pet Shrimp specializes in hardy, well-bred freshwater shrimp that ship safely and arrive in great condition.

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Tetra Fish: A Comprehensive Guide to the Characin Fishes of the Aquarium Hobby

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