A chat about medaka in a cold winter. No action ... just talk!
I refer to a Japanese KZfaq channel called こう爺 (Koji in English) about medaka. Copy and paste into KZfaq search those 3 Japanese characters to find the channel.
Koji-san who runs the channel has a video at • 今朝氷が張りました！！しかし日中は水温が上昇... which covers some aspects of cold winter conditions. It's in Japanese, but English subtitles can be generated in the Settings options. Some of the English translations are a bit strange; but understandable.