If i want to use the EI method, and i have dry ferts, do I mix with water or can I dump dry. I've read about mixing with water and keeping the mixture handy for daily dosing. However, what does the conentration need to be at?

You can dose dry fertilizers directly into the tank. Or, you can dip a cupful of water from the tank, mix the dry fertilizers in that and dump that into the tank. Or, you can take a weeks doses, mix them with water in a bottle and dose a third of that each dose, three times a week. Or, you can do the same, only dose one seventh of that 7 times a week.

Just don't pre-mix the trace element mix with the phosphates. That will cause the iron in the trace mix to combine with the phosphates and form an insoluble precipitate that just remains in the bottle as you dose the pre-mix. It takes two bottles to dose the ferts mixed with water.

If you mix them up ahead of time, keep them in the fridge. Otherwise they will start growing fungus and stuff. It's good to do no more than a month at a time.

I assume if you pre-mix in water you still go by the original "dry" amount. i.e., pre-mix 10 teaspoons fert. in 500 ml H2O and want to add 1/4 tsp fert., you add 12.5 ml of your solution?

Yes that is correct. Usually premixing is used for stuff that's hard to measure dry, like KH2PO4 to add phosphate to a 10g (the amount would be so tiny it would be nearly impossible to measure accurately dry).

I find the easiest way to do a premixed fertilizer is to first decide how much liquid I want to dose at a time. That could be a syringe full, a cap full, or something like that. For example, in my case I wanted to dose 1 ounce per dose. Next, based on the size of the bottle, figure out how many of those doses are in the bottle. In my case it is a 16 oz bottle, so I have 16 doses in the full bottle. Next I calculate how many tsp of KH2PO4 I need per dose (for example). If it is 1/8 tsp, I multiply that by 16, and that is how much KH2PO4 I put in the bottle with 16 ounces of water. Now, my one ounce dose will contain the right amount of fert for one dose.

I mix KNO3 and KH2PO4 together in one bottle, and CSM+B and MgSO4 together in another bottle. Since I dose every day, dosing both mixes each day, my mixtures are pretty weak, so they dissolve easily. And, because they are so weak I don't worry about dosing iron and phosphate on the same day.

It's also sometimes easier to dose liquids for some folks.
Whatever gets you to add the right amount basically is the method that you should do.
Liquids, dry, daily vs 2-3x a week etc

Regards,
Tom Barr

This may be covered elsewhere in the forum, but what is the maximum solubility of KNO3 and KH2PO4? THanks!

Why do you dose MgSO4 every day? Does it get removed by the plants? I always thought that once you brought it to recommended levels, it would be ok.

I have a unique setup compared to most people. I trickle water into the tank constantly, with an overflow maintaining the proper water level in the tank. Currently I drain out about 8 to 10 gallons a day, using that water for the container plants on my deck, and a planting bed below. My goal is 5 gallons a day, but it is running a bit high now.

So, I do continuous water changes, and logically need to do continuous fertilizing to maintain the levels in the tank. I'm not sure that my Mg level is low, because the water supply here varies from season to season, being largely river water (very soft) during the high river flow, low water demand seasons, and a mix with well water during other times. So, the water quality report gives a big range for all values typically found in the water.

I dose magnesium just to be sure I have some, not much, but a small daily dose. I could look up the amounts I use, but I'm downstairs, and the tank and fert bottles, with the ingredients, are upstairs, and I am a bit lazy. If you are really interested I will post them later.