A Beginner's Guide to Medaka Water Quality Management | Water Change Frequency and Green Water Usage
Tips for managing water quality when keeping medaka. This article explains proper water change frequency and methods, the benefits and creation of green water (aged water), how to dechlorinate water, and signs of deteriorating water quality.
Key Takeaways
Tips for managing water quality when keeping medaka. This article explains proper water change frequency and methods, the benefits and creation of green water (aged water), how to dechlorinate water, and signs of deteriorating water quality.
The Deep Relationship Between Medaka and Water Quality
Medaka are small fish native to Japanese rice paddies and streams, and are often called "beginner-friendly" due to their hardiness. However, if you become complacent about their toughness, water quality can gradually deteriorate without notice, leading to disease and sudden death.
By understanding the basics of water quality management, medaka can live longer and healthier lives. This article explains water change methods and frequency in an easy-to-understand way for beginners, and also covers the use of "green water," a technique unique to medaka keeping.
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What Water Quality Do Medaka Prefer?
Here are the guidelines for water quality that allows medaka to live comfortably.
Water Temperature - Ideal temperature: 16–28°C - For outdoor keeping from spring to autumn, they can generally adapt to natural temperature changes - Temperatures above 35°C in direct summer sunlight are dangerous. Use shade cloth or light-blocking nets for protection - In winter (5°C or below), their activity slows and they enter a dormant state. Sudden freezing can be fatal
pH (Hydrogen Ion Concentration) - Optimal range: 6.5–8.0 (slightly acidic to slightly alkaline) - Tap water varies by region but is generally neutral (around pH 7) and poses no problem - In environments with many aquatic plants, pH may fluctuate throughout the day due to CO2 absorption and release
Ammonia, Nitrite, and Nitrate
Ammonia is produced from medaka waste and uneaten food. Ammonia is highly toxic to medaka, and when its concentration increases, it can damage them in a short time.
Once filter bacteria are established, decomposition progresses in the order of ammonia → nitrite → nitrate. While nitrate is less toxic, its accumulation gradually worsens water quality. This is the fundamental reason why regular water changes are necessary.
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