Par intensity versus duration

Dana Riddle · Dec 29, 2018

The caveats being several. First, the ocean water off the Kona coast is likely Jerlov's Oceanic I water, the clearest of any in the world (there are no permanent streams flowing into the ocean in this section although there is one up the coast near Kawaihae.) The visibility is excellent on most days, although a rough ocean can stir up a lot of detritus and cause an astronomical number of micro-bubbles to become entrained. Second, this is a summer measurement taken close to the summer solstice. Third, it took many attempts to get the data in the first chart. Regardless of what travel brochures show, cloud cover happens like clockwork at the summit of the Hualalai and Mauna Loa volcanoes, usually around noon. So getting a completely cloudless day when it is safe to enter the water for a dive and making sure the equipment is OK in its underwater housing is a feat. I had to abandon one attempt simply because my pencil was lost.

Fredm · Jan 12, 2024

Hello everyone,

I'm bringing up this old topic because I'm wondering about my, our, lighting settings. If I understand correctly, in the vast majority of species, the saturation point is reached at a PAR of less than 300. However, most settings aim for between 250 and 350, for 7 to 9 hours a day. With one hour of sunrise, this saturation point is quickly reached, and maintained for the rest of the "day".
So I'm wondering if it wouldn't be wiser to use this simulated sunshine curve to adjust the settings, rather than something linear? In this case, we know that at the zenith, the PAR is well over 300, so how high could we raise the PAR during those 2-3 hours at the zenith? Do you think this would be beneficial for the corals? Is a curve like the one Dana's readings give conceivable in our tanks, with a peak at 450, for example, in the zone where the most demanding corals are located?

Fred