Increasing water flow ill help some. The main thing is finding a way to kill the algae or starve it of nutrients. Then it won't grow anymore. Some people have used Algaefix in their aquariums with some success, but keep in mind it's at your own risk. Some people have successfully used Kent Tech M which is a magnesium product. You would have to increase your magnesium levels to 1600 ppm for about two weeks before seeing any algae start to die. The only problem is that when magnesium gets that high, you will see some adverse effects in your inverts (snails, cucumbers, abelone, etc.)
Keeping the lights off for two days with coral is fine, but you aren't going to see much algae die off at all. Algae has to have a pro-longed period of darkness to see any results. I generally recommend keeping the lights on only 3 to 5 hours a day for two or three weeks. You'll see some die off. But, keep in mind, when the algae dies off, nutrients (Nitrate and phosphate are leaked back into the water column. So, water changes are a must, unless you have another form of nitrate and phosphate removal (GFO, Phosphate sponge, Nitrate Sponge, Algae Scrubber, etc.). If you don't remove the nutrients (algae fertilizer) then it will just grow back again.
Again, good husbandry practices play a key role. Water changes to reduce nitrate and phosphate, and to replenish trace elements. Rinsing frozen foods before feeding. Feeding the proper amounts, and varied diet. Keeping the lights on a timer for an 8 hour day. Changing your lights out when they are due. Replacing or cleaning pumps or powerheads that are no longer working to full capacity. Gravel vacuuming your crushed coral every time you do a water change. Noticing small changes in your water chemistry and responding to them... Those are all great husbandry practices that should be done.
