The sentence means: Every day, as soon as (一) Ye Xian arrived at the pond, the fish would come and show his head.
April 4, 2019
0
3
That's the character 一 (yi). It means "once" or "as soon as". The grammatical structure is 一... 就... Read the explanation here: https://www.chineseboost.com/grammar/yi1-jiu4-as-soon-as/.