If a paramecium swims from a hypotonic to an isotonic environment, will its contractilevacuole become more active or less?

Less.

Explanation:

Its contractile vacuole become less active because of the same concentration of water in both the body and outside environment. Contractile vacuole is responsible for the removal of excess liquid with the help of contraction. In isotonic environment, there is no flow water occur inside or outside of the cell due to the presence of equal amount water in both the environment i. e. cell and outside environment so due to equal amount of water, contractile vacuole become less active.