Couple questions: temperature and lighting

I have a 55 gallon aquarium with 6 T5 48'' bulbs: 3 actinic and 3 10,000 K. What is the best combination with regards to bulb selection. I have fish and soft corals.

Also, my temperature is 81 degrees. I think I want to lower the temperature to about 78. I know i can just turn the knob on by Rena heater, but should i gradually do it, say over a period of a week or something.
Also, is 78 degrees warm enough for my fish and corals?

 

78-79 is the perfect temp. I would do it gradual over the week but 81 is still in the ok range. I have metal halide so I cant help you with lighting.
Good Luck

 

I agree on the temp. as far as bulb condemnations go that is a matter of preference of how you want your tank to look, more blue more white ect.. check out this thread on bulb combos that Guitarman started.
http://www.3reef.com/forums/reef-lighting/t5-bulb-combinations-w-pictures-59447.html
it should at least give you a idea of the kind of look you want.

 

If your heater is bringing your tank up to 81º, I would just turn it down to 78º all at once and let ambient air temperature bring it down. It's not like you are putting a super chiller in place and dropping it over the course on an hour. For a 55G tank, it will take some time for it to lower that much, I would say at least 4-5 days. Temperature shock won't be an issue since you have enough water volume to let the temperature equalize naturally. And really, a 3º differential isn't much at all. Most chillers swing 2-3º between on and off cycles anyway, and that is over a few hours, you have nothing to worry about.
As far as bulb combinations, I would have a mix of 10000K and a mix of 460nm and 430nm actinics.