The ALGcontrol makes use of fluorescence excitation. This means that when chlorophyll molecules absorb light, a fraction of the energy absorbed is remitted as fluorescence. Due to the fact that algae of the same class contains a similar quantity and quality of pigments, their fluorescence excitation spectrum (with a fixed emission wavelength at 680nm) is significant. Thus, it is possible to differentiate classes of algae by their fluorescence excitation spectrum.
Other fluorescing matter (for example, DOM = dissolved organic matters measured with the 365nm wavelength and turbidity, measured with the 710nm wavelength) are detected to enhance the accuracy of the ALGcontrol.