You are going to be using very small quantities of Ferts, so it will all dissolve and stay in solution.
For me, I mix my solutions in a 1 gal
container and use that to refill the autodosers.
Not to muddy the waters further, but I actually mix a concentrated jug of solution that I then add 50mL of to a 1 gal
container to get my correct dosage. This way it takes 30 secs to mix up a new batch, and I don't have to do a bunch of careful measuring when I do a refill. My concentrate jug will last over a year before I have to drag the scale and dry Ferts back out.