I use triple threat predator spider mites. You can order them from Natures Wonders (see below). You need to apply before flowering otherwise you will get the holding substrate (grinded corn husks I believe) on the flowers and you can’t get it off. Best if used on clones and in early veg. This way you get control early on but also it takes a lot less containers to sprinkle on because your total square footage is much less. I use 3 times, 5 days apart. That way you cover the full life spectrum of the mites you are trying to get rid of. If you are already in flower you can use Neem oil up to 10 days before harvest to maintain control. See link below for Einstein Neem Oil product. Since you’re indoors, always apply the Neem oil about an hour after lights go off.
This is the best Neem oil you can get:
