Gotcha. If you are feeding heavily with low nutrient readings and showing no signs of algae, the true question is "whats consuming the nutrients?" And from my research and understanding dinos can arise from a combination of low nutrients, low biodiversity, sudden change to parameters (water and lighting), etc. Dinos are in every reef tank but are dormant until the conditions are optimal for them to compete with other microflora. From my personal experience, I believe I got dinos when my NO3/PO4 bottomed out for a good period of them in combination with setting up a new light. I'm not saying you're going to get dinos but just be aware of the ULN as most coral and normal microflora (beneficial bacteria) use NO3/PO4 for metabolic activity. Just my 2 cents.