cloudy mold in my nutrient water mix?

Alright so I mixed my GH nutes probably about a week ago now, and i was just about to finish up watering of the 2gallons I had mixed when i noticed this white cloudy mold/bacteria in the water floating around. I dumped what was left.

Its very similar to this thread, pic is a few posts down (exactly what i had)
https://www.rollitup.org/general-marijuana-growing/115994-white-cloudy-mold-nutrients.html

Im curious what it was, if its ok to water with, and if nute water spoils. I figured hydro resvoirs have nute water in them for weeks and they dont grow mold so i could leave this out.

Any advice? How long is max time to leave nutes out?

keep it in the fridge.

Not really an option for me, any other ideas?

Then only mix as much as you need...it usually won't keep unless you have something light tight to keep it in...water with nutes in it is great for algae growth...
Same issue lakes near pig farms have.

Nitrogen and well lit water are a great host for various algaes that suck all the oxygen out of the water they are in..this making it no good for drinking, or fish, or other plant life...