I just sprayed for mites two days ago. Upon first watering today, I find these on the outside of my containers (flood/drain), and they appear to be retreating from the water. Here are two pics, one of them where I first saw them, another where they are starting to climb up the stalks next to hydroton to show scale. Edit: talked to another grower locally that helped me identify them. They are water aphids.
They are ten times the size of the spider mites that i just sprayed for. Maybe 1/5th the size of a lady bug. Very easy to see.