Thank you Bob,
This why I have the +/- before each amount, for the number conscious individual that need's the crunch...
Those number's are in fact a good starting point, for any individual wanting to get a good feel for dosing the EI on his/her tank within the range's specified.
Dosing precise amount's/tweaking, based on volume specified within each tank/s size catagory is entirely up the said individual
Personally I think that the EI recommended number of 1-3 is being modest, even 5ppm P04 is not bad, and the plant's do not seem to mind it either.
I have ran 5+ppm P04 on tank's to see the result's for myself, tested with cheap kit's mind you, but they were accurate enough.
I did not see any adverse effect with a P04 reading of 5ppm, although 2ppm, 3ppm is good, 4ppm or 5ppm, is not bad.
I will do some more testing on this and post result's but my finding's so far are, very clean plant's and tank with an average 3~5ppm P04 while also maintaining a moderate level of KN03, K+ & Trace's, with highlight, C02 injection.
Actually the only downside I found, was being a bit wasteful on the KH2P04 being dosed, and some have high level's of Phosphate in thier tap water, while it is still not recommended to use Phosphate sponges, remover's absorber's, etc.
However I am not recommending people run 5ppm P04 on their tank, the +/- is thier for my protection also
that is for the individual that feel's the need to tweak his/her tank parameter's, those number's are average dosage's and a good starting point for people.
Maybe Tom will pop in and give his opinion on this also...