I know this is probably NOT what you wanted to hear...but, if they're already building webs, you're pretty screwed IMO. You have an established, breeding, multi-generational colony with more on the way. You need to catch them MUCH earlier than that. Neither I, nor anybody that I know of has been able to successfully eradicate them (without getting rid of all their affected plants...and then some) once they have reached that stage. (Super toxic pesticides in multiple releases notwithstanding).
Sorry, maybe someone else can chime in with an ancient Chinese secret remedy...
How prevalent is the webbing? (along the tops and new growth)...
If they are outside, wash them off with water and then do it again at least every other day for a few days. Their life cycle is very short, three days or so, and you must continue to wash them off as they hatch. It won't take long to get rid of them. Miteicides (s) are very expensive and you can't use them in aquaponics anyway. I've used the latest and greatest on ornamental plants and found that nothing works better than water. If you turn the leaves upside down in sunlight, you will see the pinhead sized mites scurrying. You may need a magnifying glass. Good luck.