  We investigate the fluctuations of the condensate in the ideal and weakly
interacting Bose gases confined in a box of volume V within canonical ensemble.
Canonical ensemble is developed to describe the behavior of the fluctuations
when different methods of approximation to the weakly interacting Bose gases
are used. Research shows that the fluctuations of the condensate exhibit
anomalous behavior for the interacting Bose gas confined in a box.
