Choosing the Right Colour Container for Medaka

Does Tub Colour Change Medaka Colour?

A visual guide for medaka keepers

🎏 Introduction

If you’ve ever moved your medaka from a black tub into a white bowl and thought, “Why do they look completely different?” — you’re not alone.

This phenomenon is real, and it’s one of the most fascinating aspects of keeping medaka. While their genetics stay the same, their appearance can shift dramatically depending on their environment.

Let’s break down why this happens—and how you can use it to improve your fish.

🧠 The Science: Background Reaction

Medaka have specialized pigment cells called chromatophores, including melanophores (black pigment) and iridophores (reflective cells). Chromatophore

These cells respond to environmental cues, especially background colour.

Simple explanation:

• Dark background → pigment expands → fish look darker

• Light background → pigment contracts → fish look lighter

Scientific studies show that medaka physically change pigment cell size and distribution depending on background. (ScienceDirect)

🎨 Visual Comparison: Dark vs Light Tubs

Dark Tub (Black / Dark Blue)

• Deeper, richer colours

• Stronger blacks and reds

• Lamé (glitter) appears sharper

• Patterns become more defined

Light Tub (White / Clear)

• Brighter but softer tones

• Blacks can appear grey

• Contrast is reduced

• Subtle details may be harder to see

How Colour Change Works

Dark Environment: Pigment spreads → absorbs more light → darker appearance

Light Environment: Pigment contracts → reflects more light → lighter appearance

✨ Why Lamé (Glitter) Looks Different

Lamé comes from reflective cells called iridophores, which bounce light back differently depending on contrast and lighting. (Medaka City USA)

• In dark tubs → lamé “pops” more

• In light tubs → lamé can look softer or washed

This is why breeders often use dark containers for photography and selection.

🐟 Not All Medaka React the Same

Some strains are highly responsive, while others are bred to resist this effect.

Strong background reaction:

• Tricolor (Sanshoku)

• Tiger types

• Yozakura, Miyazakura

Weak or no background reaction:

• Deep black strains (e.g. Orochi-type lines)

• Wazumi

• Some stabilised breeder lines

These have been selectively bred to maintain consistent colour regardless of environment.

🌤️ It’s Not Just Tub Colour

Tub colour is only one piece of the puzzle.

Other major factors:

• Sunlight exposure (huge impact on colour development)

• Water clarity

• Diet (live food enhances color)

• Outdoor vs indoor conditions

Medaka are highly responsive to environmental changes, including light conditions and seasonal shifts. (nibb.ac.jp)

🧪 Breeder Techniques

Experienced breeders use tub colour strategically:

• Black tubs → evaluate colour depth and contrast

• White tubs → check pattern clarity and flaws

• Blue tubs → balance between the two

Some breeders even move fish between tubs to assess their true quality.

🎯 Practical Tips for Hobbyists

If you want the best results:

✔ Use dark tubs to enhance colour
✔ Use light tubs to inspect patterns
✔ Keep lighting consistent
✔ Raise fish outdoors when possible
✔ Don’t judge a fish based on one environment

🧵 The Key Takeaway

Tub colour does not change your medaka’s genetics—but it absolutely changes how they appear.

• Dark tubs = deeper, richer colours

• Light tubs = softer, lighter appearance

• Each setup reveals different qualities

In the end, the “best” tub colour depends on what you want to see.

🌸 Final Thought

Understanding background reaction is one of the biggest steps toward appreciating medaka at a higher level.

Once you see it, you can’t unsee it—and you’ll start to realise why Japanese breeders are so particular about presentation, lighting, and container choice.