I did add two boxes of peat granules to my base layer after you had recommended keeping some organics in there, Frank. I even left a few stray leaves that "escaped" the sifting
I've seen a nice difference already....I think that may be why my Hygro corymbosa stricta is going super-red. I have to say that it works.
If you use peat granules, make sure that you put them on the very bottom! I had a few pop up and go floating merrily along with the current. Quite a few, actually! LOL! Once it's water-logged a peat granule will stay down, but my goodness! Those little dudes are very buoyant!!
About the need for some Organic materiel and Anaerobic Bacteria in the MTS mix:
"The iron has to be dissolved in order to be available to most plants. It won't dissolve unless its chemically reduced to Fe++ (ferrous ion). That requires the absence of oxygen caused by anaerobic bacteria acting upon organic material (i.e. peat). Specialized anaerobic bacteria are also responsible for the reduction of the iron. The humic acids of peat also prevent the Fe++ from being oxidized and precipitating (going out of solution) by attaching to the dissolved iron ion (a process called chelation)."