Hi BA,
Would you believe a range of (rounding out decimal points since I'm converting from degrees Celsius) 78 to 91 degrees Fahrenheit within the span of one day in summer? The longest temp plateau (5 hours, 10am to 3-ish ) averaged 84F. Corals down the reef wall naturally deal with a cooler range, but below 79F average, coral diversity and density very noticeably decreases on that reef. Still purdy though, hehe.
I could drown you with stats if certain friends would allow me. But the above range is from my own personal data and so I can freely share. It was taken on a crest, depth of about 1.4 metres at high tide, maybe 10 metres from a drop-off. I and three others basically bored ourselves to death's door in a roofed canoe parked out there for 19 hours straight with 3 temp probes and a drum type data recorder. We did catch a lot of fish that night
But I digress...
You've seemingly put your finger on the sore that our corals feel keenly:
Today's reef tanks provide poorly for them with regard to quantity and quality of lighting, temperature water motion, gas exchange, available food, general diluton of dissolved organics, and above all contextual biodiversity.
Do I advocate that you run higher temps?
That reminds me of a discussion with Kirby Adams, Rob Toonen and others on AL some months back (...I think it's been archived there). I probably run warmer tanks than either of those two --and I was the one urging caution in rushing to warmer temps!
If you raise temp AVERAGES (because daily swings are IMO vital) from the 70's, corals are more at home. They DO more things, so you have to light them better and feed them more. Then you have to have the biodiversity and water movement/volume to deal with all that digestive/respiratory waste.
Bottom line?
A stable, cooler reef beats an unstable warmer one. But...
IMHO nothing beats a stable, warm reef --and that requires great lighting and water movement/volume, full embrace of the beauty of biodiversity and the living food it can provide.
--and oh yeah, warmer temps
PS: I'll see if I can post pics of the reef I frequent, by Saturday
horge
[This message has been edited by horge (edited 09-27-2000).]