This is an article from the Aquatic Vet News – FYI.
Tag: koi
Sexing koi
To follow on from my previous post, text books will often tell you that a male koi will be slimmer and have a longer head. Female kois will have a wider, deeper body and a shorter, more feminine head.
Those in the know will also add that during the breeding season, the male fish will be rougher to touch along their flanks and over their operculae (gill covers). The females on the other hand, will have smoother skins.
Your female kois will be roeing up now in preparation for spawning which would occur over the next few months. You might notice males showing more interest in the females and will chase them when they are ready to spawn.
Are your pond fish not eating?
If they are outdoor pond fish, try feeding them during the warmer part of the day during winter.
The weather will be warming up soon and they’ll regain their hearty appetite. Be sure that your filter will cope with the increase in feed. You can check by monitoring the ammonia and nitrite levels regularly.