I may have the same bugs you are talking about, root aphids. They do not fly, they live in the rockwool/soil, and totally destroy your yield. I've had them for waaay too many harvests now and have tried EVERYTHING to get rid of them. Yes, diatomaceous does work, but only when they come up to the top. The bugs I've had are white or amber colored and you can see the plants they are really attacking by the lack of roots, the leaves droop, the leaf margins curl under, and the leaves start to die like a phosphorous deficiency. I even tried this systemic thing last harvest where you water the plant with it, it absorbs it, and then when the bugs eat the roots, they supposedly die. It can take up to 30 days for it to work and I didn't have that much time left. It didn't totally work either. These buggers multiply like you wouldn't believe and their eggs can sit dormant for months and then hatch. The only option for you--if they're the same bugs--is to dump your plants, clone them if you need to, but keep the clones far, far away from your grow space, hotbox and fog your grow space and clean everything with dish soap. The root aphids need water to survive. Fungus gnats are totally different. Their larvae are little wormy things that leave honeydew on the top of the rockwool/soil and they do also eat roots. They look clearly different than root aphids. I've had them also and they are easy to get rid of. Root aphids can be identified with the naked eye if you look hard, but usually you need a magnifying glass. Root aphids leave a powerdery mildew type substance on the rockwool/soil. Good luck!