Blacking it out won't hurt the soft corals. If you feel the need, you can run the lights for a little in the morning and in the evening... but probably no more than an hour each time. This would be the perfect time to feed your fish, but meager portions only.
Vodka dosing is a form of carbon dosing. Some people use vinegar. I used the commercial type called NO3 : PO4-X, and it helped reduce nitrates fairly quickly, but takes much longer to get rid of phosphate. Carbon dosing is basically food for bacteria that consumes nitrate and phosphate. Dosing creates a bacterial "bloom", and as the bacteria consumes NO3 and PO4, the bacteria must be removed from the water column in order to rid the system of these compounds. This is where a good skimmer comes into play. "Harvesting" is a good term for this process, as it's similar in effect to harvesting macro algae. Daily dosing will keep the cycle going, and you would typically see a fairly quick reduction in nitrate. It takes considerable longer to see significant results in phosphate reduction. I dosed about a year, and one day I decided to stop to see what happened. Nothing happened, so I guess it helped colonize enough bacteria to support my system. Nitrate and phosphate levels remained pretty low, but still higher than I wanted, and I still had hair algae issues. That's when I turned to GFO. Once I started using GFO, my nitrate levels have been undetectable, and phosphate hovers just above zero. Carbon dosing comes with an inherent risk, so if you choose to go that route, follow the directions very carefully.
