The only real, readily available way to determine if your lights are strong enough for your corals is to measure their PAR output. But the measurements have to be taken from in the water, near the locations of your various corals. To do this, obviously you will need a PAR meter. They aren’t terribly expensive, though they are somewhat cost prohibitive in an already expensive hobby, but they are worth every penny. The meter comes with a water proof probe that can be attached to an acrylic rod and placed at virtually any depth of the tank. Move the probe up and down, left and right to determine whether or not your lights are powerful enough. It has been shown time and time again that a PAR reading at or above 100 is sufficient for most types of corals. So if you are getting this reading at the very bottom of your aquarium, you should be good to go at all levels of the water column.