It can help you place corals in your tank if you know the approximate par of various areas. If you change lighting it can help you acclimate your tank to the new lights. You can judge bulb life, and the differences between different bulbs, as well. Whether it will be used enough to be worth the money is up to you. I plan on buying a sensor and hooking it up to a multimeter. For $140 I think its worth it, at $300 not so much.