Effect may be doubted

I certainly, as purchased many others, this product in order to improve the water quality. Whether that actually happens, I can make difficult to here. It does not seem to hurt my fish (60L Aquarium) but whether it improves as the water values, unfortunately I could not prove by measurements.

Meanwhile I run 2 tanks again without the product and have not noticed any degradation.
-> Found no improvement in me
-> Not advise