The strength of the fragrance depends on a number of factors, including the size of the room, ambient temperature, humidity, and airflow. To increase the strength of the fragrance, I would recommend trying a few things:

  1. Make sure that all the reeds are in the bottle, as more reeds will diffuse a stronger scent.
  2. Place it in a warm part of the room that has good airflow, such as beside a warm air vent going into the room.
  3. Flip reeds more often for a stronger scent (every 1-3 days).

To make the scent lighter, use few reeds in the bottle and flip the reeds less often (every 1-2 weeks).