My corals look the best when my phosphate is around .01-.02. Using zeovit it is easy to reduce phosphate to very low levels. I will say that my best indicator of phosphate is my orange monti cap, when the phos. is too low it looks almost pink. At this point I just feed the tank a little more. I truly think if your phosphate were zero your coral would die, there is some needed to build coral, too much will inhibit growth.