How much are you feeding? You definitely don't want all of your nutrients to be 0. That's why you are having dino issues. Doing water changes will just reduce nutrients more. Of you have a filter sock stuck out all of the dinos into that over a bucket. Then just dump the water back in. You don't want to raise just nitrate in a tank either because corals(especially sps) need a little bit of nitrate and phosphate. There is a good webinar mr. Saltwater did on algae and dinos.