I mix vinegar with Calcium hydroxide and RO for my auto top off. I started with 1 cup vinegar, 1/3 cup calcium hydroxide, and 5 gallons RO. This caused my Alk to increase to 11 and the nutrient level in my tank to fall to 0. My coral started growing very fast but it also caused them to loose much of there vibrant color. The new coral growth was pastel. This also caused my refugeum algae to loose its color.
I dialed my vinegar down to 1/3 cup, 1/3+ cup calcium hydroxide, and 5 gallons of water. My coral and algae has colored back up and my coral growth is still vey good.
Vinegar is a great tool but you need to get the dosing right or it could damage your corals. Be careful and take it slow!