I don't know how sold you are on your beneficial bacteria, but I am pretty sure zone will do a lot more to combat bugs like that.
Dutch Master Zone will zap larva so I hear. Now I haven't tried it first hand because I've never had bugs in hydro yet, but I do use Zone and I have had no problem in my root balls even with terrible temps in my rez.
I am no bug expert, but I think those may be thripes (not positive). They're definitely not gnats, if they were gnats there would be larva on the roots, not fully mature bugs. Fungus gnats are one bug I do know quasi-well. Adult gnats lay eggs in your medium. The eggs hatch and the larva chow down on your roots. Once the larva turn into adult gnats they live another 13 days, this is the time they lay more eggs in your larva. Adult gnats do not eat, so the only damage adult gnats can do is lay more eggs and make more larva. But whatever they are Azamax should take care of it. I've only used Azamax in soil (for both spider mites and fungus gnats) and it worked wonderful. I've heard of people using Azamax in hydro, but you may want to double check before investing in a bottle of Azamax, it's not super cheap.