Hi all. I made quite a large lake from the island in the end.  In depth is average 15 blocks and all water are sources of water, no falling water.

Btw. it is on the server with version Spigot UNSTABLE 1.15.2

I have already discovered the problem since 1.14

I think i tried, original vanilla minecraft server, Spigot, and it was always the same. 

I wanted to put there many tropical fish as i can find. When i had there 200+ fish, then i find out that all fish swim towards North/West.... I tried to put them on the other side but fish always swim slowly  towards North/West.. They can do it  all in an hour. Turtles swim normally anywhere. Every time all the tropical fish gather in one place... Its so annoying..

In a small aqarium you won´t notice this..

I would like to fish swim anywhere, can it be solved in any way please?