Hi David, I have never done darkness before but this year Im on it, I have been on it for 2 weeks..I was told to give garlic in the water after 4 days on darkness then every other day for a week which I did, I have stopped it now and just give a bit of garlic oil on the corn..which my birds always have anyway on a monday, and the young birds are falling to bits feathers everywhere after 2 weeks, was it the garlic not sure but they are moulting rapidly.