I'm a total beginner when it comes to video editing and would like to overlay two shots I made.

On one a girl is dropping chunks of fish into an aquarium, on the other she is dropping real fish. I made the shots with a tripod from a fixed position and so the aquarium is a t the same place in both sequences. The girl is at the side of the aquarium the whole time.

So what I want to do now is to replace the aquarium with the fishchunks withthe one with the life fish, so that it looks like she's dropping the chunks and when they touch the watersurface they turn into fish. (i made the shot from an angle, so there is a reflection on the water which gives some room for sloppiness, as the fish and chunks disappear on that part

Can anyone please explain me how to do it (best in Premiere, so I don't have to cut out picture by picture..)

Thank you all in advance