Vinegar/Vodka dosing

[FragIt Dan]

That's a tough one, looks like you are doing everything right. Only thing that stands out to me is the DSB, which might be a nitrate factory. I started to siphon parts of my DSB out with water changes (maybe just 5 or 10% of the sand) and washing it, then putting my clean water into the bucket with the clean sand and siphoning it back into the tank (this keeps the sand from getting all over the tank when you put it back in). The water that came out with the sand was pretty nasty, so I think this helps. I try to do this with some of my water changes now. Just be careful you don't undermine your rockwork and collapse your reef! I also only feed fish once or twice a week, corals are a bit more often though.
Dan