Kicked the chemistry part of my brain into gear and worked with the rota.la calculator (it is just excellent !) To get started, I've decided to do it like this :
I've calculated 3 different macro fert levels for my tank, low, medium and high, taking into account a theoretical "self-production" of the tank. In the beginning, I'll make up weekly doses in 100 ml bottles, with the weekly supply. This way, all I have to per week is use up the bottle in three dosings. And it won't matter so much if I get too much or too little, and less dry ferts will be wasted if I get it wrong.
Observing the plants for 2-3 of weeks, I can then assess growth and adjust to the next level if/when needed. Weighing out stuff doesn't bother me at all, I'm used to it as I make pretty much all my own skincare products. It is quickly done while I'm busy anyway during waterchanges. Later, when I know more about how my own tank and plants (and fish !) react, I'll make more longterm fert solutions.
I'm still not sure about traces. The closest I can find to compare mine with is the Miller's Microplex, except mine hasn't got all that copper. And 38g/l of iron isn't all that much after all...just 3.8%. But then again percents are difficult to work with when you don't know how it is calculated (w/w or w/v). Think I'll target the right ammount of Mn, and then supply with iron from another source till my current supply is out. Then I'll look into buying some Plantex CSM+B.
Humans may rule the world...but bacteria run it..