8. More ammunition for your arsenal.
Bti (Bacillus thuringiensis israelensis) will kill fungus gnats but it needs to be applied to the soil over a four or five week period. Some people swear by diatomaceous earth, but the jury is still out on that one, because while it will eradicate the larvae near the surface, it can’t get at the ones up in the tangled roots. Some people dust the top of their soil with cinnamon to discourage the adult from laying her eggs there and some add fine sand to the tops of their plants for the same reason. It is said that the addition of coir (coconut husk) to the soil is a deterrent to egg laying, but if you do this, be very spare in your watering.