with all the test kits out there, ...
i'm looking at what i can find about dosing our tanks and running into a big of a problem.
it's all in ppm & mg/l type quantities, ... based on knowing what's in there to start with.
of the 18 or so nutrients i've seen test kits for half of those, ...
i'm kinda thinking as great as this scientific chemist method is, ... if you don't know what is going in, and during water changes your estimating what is being removed (so you don't really know what the plants have consumed)
correct me if i'm wrong, ... but if you don't know what your plants are consuming, and you don't know what's left, and you don't know what you are removing, ... and all this is guestimating...
water changes at this point are to ensure nothing becomes toxic without really being sure, again more guestimating
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doesn't it make more sense to understand deficiency symptoms & nutrient interactions (so you know what is needed, and what could lock out or inhibit other nutrients)
the first there is a so-so knowledge base (from various resources and forums)
the second (nutrient interactions) - i can find enough for terrestrial gardening, and forums stress 'don't blindly add X because you may be causing problems with A, D, & Y, ... but those interactions aren't talked about in much detail.
makes it hard

unless others have resources or information on helping sort these interactions and desired levels out.