DO NOT KILL THESE
They are Hypoaspis Miles
They are a GOOD predatory mite to have around as they eat both THRIPS LARVAE and FUNGUS GNAT LARVAE.
They will colonise in the top inch of your Soil and if there is no pests for them to eat they can also feed on DECAYING matter in your soil (this is a good thing!!!!)
I SAY AGAIN DO NOT DESTROY THEY ARE GOOD TO HAVE AROUND.
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J