Remember:
Most of the species of corals found inside a reefers aquarium come from zones located inside the Tropic of Capricorn and Cancer. Inside these zones, sunlight is guaranteed to be about 12 hours per day. By limiting the amount of light to your specimens, your basically starving them of one of their vital food sources. Personally, I would never tell anyone who houses corals, to go any less then 8 - 10 hours of light per day, minimum. Instead of limiting their food source, you can always raise your lamps higher, by about a foot or so and then slowly drop the level a few inches per week until all inhabitant are acclimmated. Another suggestion is to place a few layers of fine mesh vail in-between your lights and the top of the aquarium. After 1 week, you can remove a layer of vail until all of it has been completely removed. This will absorb light intensity enough to where your corals will be content and still prosper.
Low frequency, long wave length light is a precursor to a bad algae break-out. Oh course, fueling the algae with a high consentration of PO4's and a large build-up of DOC's will only insure that a rough time is ahead. Algae needs more then light to survive, so one must look at other reasons why the outbreak has occured. One that must be acknowleged and dealt with properly to rid yourself of the nusience. A chem check with a good test kit is crucial in determining the cause.
A good reference to check are:
PO4's
Calc and Alk levels
Mag Levels
PH (am & pm)
Borate & So2 (if available)
Ammonia, Nitrate & Nitrite
If your running a skimmer, is it producing skimmate frequently, or occassionaly?
Feeding habits, quantity, and variety of foods
Type of H2O added
Look and smell of the overall system
All of these items listed above can help you figure out your aquariums status and overall health.
Personally, I never do water changes. Except for the occassional quarterly 5 gallon replacement of new salt water, to replace supplements that I can not easily obtain. I DO NOT sugggest this for ANY NEWBIE entering the reefing world. Experience and time will dictate how your husbandry will evolve. Remember, coralline algae is a great barometer of a healthy, thriving system. Time and Mother Nature will do the rest.
I hope this helps...