I have the red sea 90 and just did a review on it. I have 1 red sea reef led 90 on a 40 gallon breeder with hammer lepto chalice ricorda and acropora the app is great and you will not be disappointed with all the features other lights do not have such as on and of timer sunrise sun set acclimation mode for corals cloudy weather and staggered sun raise for multi lights synced. for a 75 gallon tank 1 light would work but if you rely wanna get into sps( acropora ) you would want 2 of the reef 90. they are cheaper than the Kassile lights also. sorry for spelling im buzzed right now... =]