This is a question that I feel doesn’t come out often enough. Everyone seems to be so preoccupied with which fixtures put out the most PAR and how to get the most PAR over their tank that I think, in many cases, they don’t even know how much they need. For starters, it is most likely not as much as you would think. The saturation point of many hard corals is above 500, but they grow great much lower than that. Even the most light demanding of corals can, and will, grow pretty quickly in the 250 to 300 range, and lower light demanding corals are even more shocking. I’ve seen it said that almost no coral will grow at levels of below 100, but that is completely un-true. Most soft corals, some LPS and all chalice will grow very well at PAR levels all the way down to 50!

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