Vimes, 6 months ago I had the same issue w being unable to eliminate them entirely for ages. Putting a layer of sand over soil in pot was what finally completely resolved it for me (in addition to continuing all the other stuff you mentioned).
I had the same issue w being unable to eliminate them entirely for ages. Putting a layer of sand over soil in pot was what finally completely resolved it for me (in addition to continuing all the other stuff you mentioned).