Careful observation is an important skill in science.
Good observation includes having a question in mind while looking, and recording information in a clear way. Different pairs of students should compare their results after several days to look for daily patterns. Fasten the clear plastic sheet to the outside of the largest side of the aquarium. Using tape or a marker, mark a grid of rows and columns so a fish's location can be described easily. You may wish to describe boundaries for front and back of the aquarium, too.