>>73963These are great preventative measures imho, but in my experience rarely stop an already established gnat infection.
>>73982>>73930There is no end to my hate for fungus gnats. Chemicals are your friend though, you just have to know which to use when and avoid the gross over-usage that seems to be the standard nowadays.
I advise a pyrethrin-based insecticide. These are plantbased and completely biodegradable. Google up on them; I found them interesting enough to write my master thesis about them. Depending on your growing conditions they decompose in a few days or a week. This might necessitate multiple applications though. Over here it can be found in most gardening stores; they often get marketed as 'bio-insecticide'; check the label or packaging.