Guppy Tail Shapes Explained: From Fan Tails to Double Swords

When you walk into a fish shop, you usually just point and say, “I want the Red one.”

But if you look closer, you will see that the “Red one” might have a triangle tail, while the “Green one” has a fork tail.

Breeders have spent 100 years engineering these shapes. Understanding them helps you pick the right fish for your tank (and avoid the ones that die easily).

Here are the main categories.

1. The “Standard” Shapes (What 90% of Shops Sell)

These are the most common fancy guppies. If you buy a “Mosaic” or “Cobra,” it usually comes with one of these tails.

A. The Delta / Triangle Tail

This is the classic.

• The Look: When the fish flares, the tail forms a perfect triangle with straight edges. It looks like the Greek letter Delta (Δ).
• The Vibe: Sharp, clean, and impressive. This is the standard for competitions.

B. The Fan Tail

• The Look: Similar to the Delta, but the edges are curved and rounder, like a traditional hand fan.
• The Vibe: Softer and more flowing. This is extremely common in mixed “assorted” tanks.

C. The Round Tail

• The Look: A short, circular paddle.
• The Vibe: This is the “Retro” look. It’s very close to the Wild Guppy shape. Because the tail is short, these guppies swim much faster and are healthier than the big Delta tails.

2. The “Exotic” Shapes (The Cool Ones)

These are harder to find. You usually have to go to a specialized breeder or a high-end shop to find these.

A. The Lyretail (The Rock Star)

• The Look: The middle of the tail is short, but the top and bottom rays are long and curved. It looks like a “Lyre” (an old musical instrument) or a wishbone.
• Why buy it: It looks incredibly elegant.

B. The Double Sword

• The Look: Two long, straight spikes sticking out from the top and bottom of the tail.
• Variations:
  • Top Sword: Only the top spike.
  • Bottom Sword: Only the bottom spike.
• Why buy it: These fish look like fighter jets. They are usually very active swimmers.

C. The Spade / Cofer Tail

• The Look: Shaped exactly like the spade suit in a deck of cards. Pointy at the end.
• Why buy it: This is the signature shape of many Endlers and wild hybrids.

3. The “Drag” Factor: Why Tail Shape Matters

This is the part most guides skip.

The bigger the tail, the harder the life.

Imagine trying to swim while wearing a wedding dress. That is what a “Delta Tail” or “Half-Moon” guppy feels like.

• The “Parachute” Effect: A massive tail creates huge water resistance (drag). The fish has to wiggle its whole body just to move one inch.
• The Exhaustion: Big-tailed guppies get tired easily. If the current in your tank is too strong, they will die of exhaustion.
• The Target: Big tails are slow. This makes them easy targets for Tiger Barbs or even hungry Tetras to nip at.

Shop Guy Advice: If you have a tank with strong flow or aggressive tank mates, buy Round Tails or Swordtails. They cut through the water like knives. Keep the Delta Tails for slow-flow tanks.

The Shop Guy’s Take

Don’t just buy the biggest tail you see.

• Big Tail (Delta/Fan): Beautiful, but delicate. Needs calm water.
• Small/Split Tail (Round/Sword): Fast, tough, and active.

If you want a fish that swims all over the tank, get a Double Sword. If you want a fish that floats around looking pretty like a painting, get a Delta.

Summary Table: Tail Shape vs. Care