I have always been told, both in print and in person, that it is a bad idea to dose our tanks with micros at the same time we are dosing macros. This is said to be because the iron and phosphate will combine to form insoluble iron phosphate, which will not be available to the plants. However, I also know that the metal micronutrients, like iron and copper, are always in a chelated form in the fertilizer mixes we use, like CSM+B. I believe that chelated iron will not combine with phosphates - that is a primary reason it is chelated. "Metal chelate compounds are common components of fertilizers to provide micronutrients. These micronutrients (manganese, iron, zinc, copper) are required for the health of the plants. Most fertilizers contain phosphate salts that, in the absence of chelating agents, typically convert these metal ions into insoluble solids that are of no nutritional value to the plants. EDTA is the typical chelating agent that keeps these metal ions in a soluble form." (https://en.wikipedia.org/wiki/Chelation
not the best source, but it is what I found on Google.)
Which is correct? If I dose CSM+B and KH2PO4 at the same time do they form iron phosphate, or does the chelator protect the iron from the phosphate?
A second warning we all get is that we can't make a liquid mix of all of the needed ferts, NPK and trace elements, which include iron, for the same reason. Is this true? Does the chelator also protect the iron from the phosphate in the much higher concentrated mix in a liquid fertilizer? Does anyone have a link to an authoritative discussion of this?