I think I have fungus nats

I think I have fungus nats. I got some fossil shell flour today. How much do I sprinkle on top of my coco coir before watering? And will it kill beneficial bacteria?

Never heard of fossil shell flour. I used a product called mosquito dunks as well as a soil drench with a dilute neem oil solution and it did the trick. I used 3-5 ml per gallon for neem. Maybe someone else has experience with that stuff.
Good luck killing those bastards!

apply the dust the day after u water, if u water while the dust is on the soil it will cake up or wash away rendering it useless spread enough on that there is a thin layer across the whole top of the soil. Get some hanging sticky traps, make sure they are the baited kind, they work wonders. let ur coco dry out a lot between waterings as eggs can only be planted in wet soil, a week of dry soil will decimate there numbers