Kohaku Koi Swordtail Wagtail

Kohaku Koi Swordtail (Wagtail)

Introduction

The Kohaku Koi Swordtail (Wagtail) is a stunning freshwater fish featuring a vibrant red-and-white pattern inspired by traditional Japanese Kohaku Koi. As a livebearer, it’s energetic, easy to breed, and a great choice for both beginner and experienced aquarists. The “wagtail” name comes from its bold red tail fins, which contrast beautifully with its white body and red sword-like extension in males.

Origin

Originally developed through selective breeding from wild Swordtails native to Central America, especially from Mexico, Honduras, and Belize.

Scientific Name

Xiphophorus hellerii (Kohaku Koi Wagtail variant)

Lighting Requirements

Moderate – Bright lighting enhances their vivid coloration, especially the red hues.

Care Level

Easy – Very hardy, adaptable, and well-suited for beginner aquarists.

Preferred Water Parameters

• Temperature: 22–28°C (72–82°F)
• pH: 7.0–8.2
• Hardness: 10–25 dGH

Can tolerate a wide range of water conditions, but thrives in slightly alkaline water with good filtration.

Placement

Midground to Top – Active swimmers that spend time throughout the tank, especially near the surface.

Growth Rate

Fast – Reaches up to 3.5–4 inches (9–10 cm) with proper care and feeding.

CO₂ and Fertilizer

Not required – Kohaku Swordtails do not rely on CO₂. However, live plants in the tank will benefit from basic fertilizers.

Potential Problems

• May nip long fins of slow-moving tankmates.
• Males can be mildly territorial—keep a 1:2 male-to-female ratio.
• Prolific breeders—may overpopulate if left unchecked.

Compatible Fishes

Excellent community fish when paired with peaceful species such as:

• Platies
• Mollies
• Tetras
• Danios
• Corydoras
• Snails and peaceful inverts

Avoid mixing with aggressive or fin-nipping species.

Other Suitable Plants

• Water Wisteria
• Hornwort
• Amazon Sword
• Java Fern
• Duckweed or other floaters for shade

Tropical or Cold Water?

Tropical – Requires consistent warmth and thrives in standard tropical freshwater setups.

What Fish Can Eat It?

Too large for most small fish to eat. Fry (babies) may be eaten by adults or other tankmates if not separated or provided with hiding places.

A Fun Fact

The “sword” tail in males is not only decorative—it’s used during courtship displays to attract females. Despite their bright colors, Swordtails are fast swimmers and agile enough to avoid most tank aggression.