I saw that movie on TV sometime in the late ‛90s or early ’00s.
It is some sort of fairy-tale for young people. I think the main character was a girl. Perhaps there was also some witch or sorceress character.
I remember there was an episode where there was an eel in a bathtub, and later it grew a lot in the very same bathtub.
Although this is probably not very helpful, but I also remember a moment, where there was a panoramic view from some high point (perhaps from a high floor or a roof of a building) during a sunny summer day, that showed an articulated Ikarus bus passing through some residential area.
I also think there were some inscriptions in Latin script, which, together with the Ikarus bus makes me think it was filmed in a Soviet or post-Soviet country, like Czech/Czechoslovakia or something like that.
I think the fish was actually a catfish, not an eel.
Could it be The Water Horse: Legend Of The Deep?
Definitely not.