Here is more information that contradicts your logic on the relationship between nitrates, phosphates, and Dino’s.
“nuisance dinoflagellate blooms is to put a stop to the problem that allowed them to arise in the first place—excess nutrients. As mentioned earlier, the safest and surest course of action here is to increase competitive pressure on them by increasing the densities of beneficial algal species. The enlightened aquarist can carry out a highly effective multi-pronged attack with the use of high-end live algal products such as
Ocean Magik. This product incorporates a blend of several species of algae that actually nourish phytoplanktivorous aquarium animals (such as many corals, clams, sea cucumbers, etc.) as they sequester nutrients such as ammonia, nitrate, phosphate and silicate directly from the aquarium system water.”
Source:
https://www.algaebarn.com/blog/phyt...croalgae-to-control-nuisance-dinoflagellates/