Holly shit !!! That guy answered my question , I was looking for. I'm quoting:
Mosquito dunks , are very effective way to kill gnats and it's eggs rapidly ! Early stages or not.. It's a great product !!!
Gognats is not compatible with microbes and does not kill many gnats, it just repels them. Try mosquito dunks, which contain a specific bacillus strain that targets gnat larvae and makes them deathly ill. You can add drunks to a tea brew or just soak them in distilled water and drench the soil. Consider adding a layer of sand to the top soil. Combine this with sticky yellow traps and remove all potential breeding grounds in other areas of the house. (cat boxes, drains, trash, old food, ect)
Mosquito dunks , are very effective way to kill gnats and it's eggs rapidly ! Early stages or not.. It's a great product !!!