Dorothy,
Those fungus gnats are truly tough and pesty.
I've been fighting them for ages and while they are reduced in numbers, they're still here.
As a fast to get hold of fix mix one part hydrogen peroxide (3% solution) with four parts water and thoroughly drench the soil.
The soil may fizz but the plants will survive. Only problem with this method is that hydrogen peroxide will also kill some soil enzymes.
To catch adult fungus gnat flies, use yellow sticky cards in the planters.
Also mix a couple of tablespoons of vinegar with a little liquid dish soap and a little water in a dish and the adults are attracted to that.
There's more here:
http://howtogetridofgnatsinthe...
