Green Water vs Fresh Water for Medaka Fry

Written by SNR MEDAKA USA

Why Does Green Water Form?

• What’s in green water?
• It forms due to the growth of microscopic algae
• Green water is beneficial for medaka fry

What Accumulates in Green Water?

• Ammonia accumulates over time
• Oxygen can become depleted
• Medaka fry in new water grow faster

Green Water or Fresh Water?

What’s best for medaka fry?

Each option has strengths — the key is knowing when and how to use them.

From My Experience:

• Green water = survival
• Fresh water = growth

💡 Tip: Maintain balance. Let it be green — but not stagnant.

0–7 Days (Hatching Stage)

• Keep in green water
• Full of natural food (algae, infusoria)
• High survival rate

After 1 Week

• Start partial water changes
• Or move to a clean water tank
• Promotes faster growth & better health

Should Fry Remain in Green Water?

• Keep fry in green water until they emerge
• Move them to new water as they grow larger