It has helped me keep my corals both SPS and LPS alive and thriving for 8 years. If you have 4000 ft candles at the lamp and 40 ft candles at the bottom of your tank when new. And then a year later 3500 ft candles at the lamp and 35 ft candles at the bottom, to me this is a good way to measure lamp fade/loss. Oh and by the way your lamps could loose 50% tomorrow and it would not be noticable to the human eye. Having some kind of meter is better than no meter at all.