[Zorfox]

The numbers in your first post look good with the exception of K2SO4. That dose exceeds the solubility of K2SO4. That said you don't need to dose a full 7.5 ppm of K through K2SO4. The KNO3 and KH2PO4 both have K in them. This is usually enough without dosing extra potassium although it won't hurt anything if you want to add a little more.

Below are the EI doses for a 500ml solution and 30ml doses. If you want to add the K2SO4 then adding 2 tsp. will account for what's not in the others.

KNO3 7 tsp. (7.69 NO3 and 4.85 K)
KH2PO4 1 tsp. (1.35 PO4 and 0.55 K)
Plantex 5 tsp. (0.48 Fe)

K2SO4 2 tsp. (1.98 K)

 

[Zorfox]

The solutions you listed from him/her are good as well. The difference being the dose, his is 15ml and mine are 30ml. It appears the user you are referencing is accounting for the potassium difference as well. 4 tsp. in 500ml using a 15ml dose provides roughly 2ppm of K. So essentially you can use either one you listed, they are both the same except for the dosing size.

If you want to convert a dose to teaspoon select the result of my dose in the section labeled "I am calculating for". Then you can enter teaspoon measure until you arrive at the dose you want. Just get close this isn't an exact science.

If you don't know what ppm a dose should be select "the Estimative index". The target nutrient will be listed in the result i.e. "To reach your target of 7.5 ppm NO3 you will need to add 70.98 g KNO3 to your 500.0 mL dosing container."

Basically the targets are
7.5ppm for NO3
1.3ppm for PO4
0.5ppm for iron
7.5ppm for K

That 7.5ppm for K is mostly provided in the KNO3. I don't think you would see a difference if you left out the additional K but as I said it won't hurt to add it just in case. The amount of K provided by KNO3 and KH2PO4 will also be listed in the results. So that covers the macros, NPK, and the rest. The rest coming from Plantex and targeting iron for a dosage. The only two left is magnesium and calcium which are your GH. So if you have a GH over say 6 dGH you don't need to worry about these. If you have less adding GH booster will account for them, including potassium if using Seachem's. If you have low GH add enough GH booster to raise GH 1-2 degrees at water change. Make sense?

 

[Zorfox]

Thanks for the link Positron. That was a very interesting read. It certainly does suggest that excess iron can be harmful to some plants. I didn't read any of the references for the article yet. The article on it's own clearly shows various toxic levels for some species. We need more information of this nature to determine maximum nutrient levels. The list of micro nutrients can get quite long depending on the micro mix being used. Having a minimum and maximum range for all of them would prove invaluable.