Sorry,
We have a Quantum Meter calibrated with a 100' cable and take readings at the same patch reef every time we go out to our live rock/coral farm, (a couple times a week) and have been taking them there since 2003...I have NEVER gotten the same reading at the same patch reef with my sensor in the exact same place at the same time of day...I always hit it at 2:30PM..and If I am early..I wait.. If I am late..I wait until another day.
Light is NEVER, a stable factor in the wild, never the same from day-to-day or hour-by-hour.
Light attenuation or extinction is greatly effected not only by passing clouds and/or moisture in the atmosphere,...but more over by the constantly changing size and shape of the lenses, (the ever changing water surface), not to mention TDS that are also in a constant state of flux.
I can't even get the meter to stop jumping from it's lowest to highest readings on the calmest of days in situ.
I can take the exact same meter back to our lab,... put it into any one of our 14 systems with as much surface motion as I dare to implement within a closed system I ...CAN ALWAYS get a stable reading even with lights moving, via fans and light movers.
Not trying to be a Know it all jerk... I just live in closer proximity to a real reef to most reefers do, and I scrutinize the differences, (between captive and wild conditions) all the time...with a vengeance.
Alkalinity+Calcium levels stay the same only...temp changes all the time, salinity fluctuates on a yearly cycle,. dietary intake is never the same due to seasonal cycles of nature.
one example; every year on one evening coral will spawn here in the Florida Keys,(there are a few different spawning events associated with different species.. however) on those evenings...when the water column fills with sperm and egg packets..or in the case of brooders, gametes...the fish, squid sharks,everything!.. goes crazy consuming all of the small protein bundles in front of them.
A week before the weren't eating any coral larva... there wasn't any in the water column..... they were eating something else.
Our little closed, high nutrient, bonsai systems are nothing like the wild on so many levels,...I believe it dangerous to compare the two.
Mother Nature doesn't have to worry about potentiometric hydrogen ion concentration...(we do), her system is big enough and constantly receiving light somewhere.-Dave
Don't get me wrong..stability is UBER important our closed systems...but not because your animals were living in, that before they were collected or aquaculture.