Of course low phos and low amonia nitrate can cause problems in acros. Zooanthalae algae is just another plant. Plants need amonia nitrate and phosphate to grow. Too much results in browing from too much zoanthale production and way too much can be toxic and fatal. Same thing with fertilizing a garden add to much fertilizer and you "burn" the crop and nothing will grow until the levels drop back down. Look at the zeovit system specifically designed to maintain super low nutrients. Corals were rtn'ing in many of these systems due to a lack of nutrients. They learned that you need to feed the corals as well if your going to run a low nutrient system that is why zeovit systems require the use of amino acids and coral foods, to keep the corals from starving. The advant in tech hasnt done much in the way of helping to progess the thinking in the way we keep sps. It used to be with old skimmers you had to maintain low bioloads and feed lightly to keep acros happy but with many of the new excellent skimmers and ways of keeping ultra low nutrient systems (biopellets, carbon dosing, zeovit, GFO, etc..) People dont realize that they are starving their zoanthale in their corals. Try feeding a little more the worst that can happen is a small algae bloom telling you to back down a bit. Just my .02.
