Regulating Temperature in the Greenhouse

25'C is the temperature we desire in greenhouses. Under 20'C is too cold, over 30'C is too warm.
To keep it warmer we filled one bathtop and several buckets with water which warms up during the day and releases warmth during the night.
To cool it down we open the door as soon it gets over 25'C.
Termometar is of great help.