In this study, ideal free and harmonically trapped Bose gases confined by two plates in the x-y-plane in-between distance d are considered. The Casimir potential is obtained from the grand canonical potential of these quantum Bose gases for the Zaremba and the anti-periodic boundary conditions. The Casimir force is then obtained for the Bose-Einstein condensate phase T ≤ T c and for the non-condensate phase T > T c. It is shown that Casimir forces are repulsive for these boundary conditions. Additionally, it is shown that Casimir forces exponentially decay in the non-condensate phase T > T c with the decay lengths. These decay lengths were discussed and compared for different boundary conditions. As a result, new results are obtained for harmonically trapped Bose gas and the free gas results are compared with previous results.