idealy, you should research an area where you want to get species from... fiji would have much different conditions than carribean species. .. deep water species also would idealy want specific paramaters are are much more sensitive to sudden changes in temp/salt/etc...
but, the majority of us usually get a mishmash of species for our tanks and thus we need to use some type of average...
anywhere in the average guidlines are fine, so long as there are no sudden changes in your paramaters...
IMO.....
the warmer the water, the quicker the organisms metabolism, and thus would require more food and nutrition but you would have quicker growth... only problem is, the warmer your temp, the less 02 can be saturated in your tank...
so.. whereas the carribean waters get as hot as the mid to high 80s in the summertime, and as cold as the mid 70's in the summer, the change takes place over a 6 month period of time.........
now what would be interesting is to know if someone has tried changing the temp this drastically over the years and have had any success.... maybe this is what we would need to do in order to get some of our corals to propegate... sorta like changing the light cycle on plants to make them flower.... i think 12-14 hours is growth cycle, and 8-10 hours is flower stage... but then again, i guess it all depends on why types of plants... but this is a saltwater forum.. so back to the topic.....
Personally...
i keep mine at 78 +- 1 ( i am still playing with my thermomiter.. but will try and keep it at 78...) I chose this temp because without the heater, my MH warm the tank from 76 to 78 by the end of thier shift.... so i just want the heaters to maintain this temp during the night... because two degrees is high fluctuation
but, you can change your temp from say 80 down to 76..... (you may want to do this during the winter months)... but the change should take you about 6 months... just like in the natrual ocean.