This hydrometer helps me to keep my plants at optimum moisture levels throughout the week. I use it daily for new plants and weekly for plants that I've had a while. I only gave it 4 stars because I still haven't figured out the sensitivity of the light meter yet. It seems to show my office as being low light when it gets a lot of light from outside (surrounded on 3 sides by windows). I also do not see a difference in light on the meter between rooms.