How to Distinguish Male and Female Medaka and Simple Sorting Methods

Let’s learn how to distinguish male from female medaka! An easy guide even for beginners.

To enjoy breeding and spawning medaka, the first thing you need is to be able to identify the males and females!
The method to distinguish medaka is simple and very easy.
Along with the method to distinguish between males and females, we will introduce a recommended method of sorting using a fish net.

**How to distinguish male and female medaka**

The distinction between male and female medaka is made by looking at the dorsal and anal fins. Let’s check with an image!


This is a male. A distinctive feature is that the dorsal fin is jagged, and the anal fin is shaped like a parallelogram.
As they grow, the anal fin becomes more noticeable from above, making it easier to determine if it’s a male.


This is a female. A characteristic feature is that the dorsal fin is rounded, and the anal fin narrows toward the tail fin.

**When can you distinguish them? How do you distinguish fry?**

It is difficult to distinguish medaka at the fry stage.
By about three months old, as their bodies mature, differences begin to appear, and that’s when you should distinguish them.
In slim individuals, it is difficult to distinguish, so make sure to feed them well to promote growth.


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