Pre-mix nutes

I use Fox Farms and was wondering if it would be ok to pre-mix my nutes and cal-mag in a canister and then just adding it to the water when I am ready to feed? I usually mix up 5 gallons at a time and it would make it much easier.

Has no one ever tried this? Also is there anyway to store unused mixed water for future use?

You don't want to premix nutes and leave them in a jug. The various salts can precipitate and form solids. That's why liquid nutrients in concentration come in different bottles. You can store unused mixed nutes in some kind of reservoir with aeration or a small pond pump on the bottom to keep the solution moving around preventing precipitation of the salts. That's what hydro growers do.

What is a Precipitate?
In chemistry, a precipitate is an insoluble solid that emerges from a liquid solution. The emergence of the insoluble solid from solution is called precipitation. Often the precipitate emerges as a suspension.

Precipitates can form when two soluble salts react in solution to form one or more insoluble products.

soluble salt 1 + soluble salt 2 → insoluble salt (precipitate)

https://www.chemicool.com/definition/precipitate.html