Fungus gnats can be a real menace in an otherwise trouble-free hydroponic system; these are small dark flies that have quite distinctive wings and long legs. Since it belongs to the Sciaridae family, it is also known as sciarid flies. These are generally weak fliers and tend to hover near the plants always.
Females generally lay the eggs when the media is wet and moist like in a potting mix; the larvae can be identified by its black head and white or transparent body and cause a lot of damage to the root systems. Killing fungus gnats are very important or these tiny bugs can ruin your entire yield in no time at all. You can visit this site if you are looking for beneficial nematodes for fungus gnats.
It is important to control the spread of these bugs as the larvae can feed on the young cuttings and seedlings. It can also promote the growth of other plant pathogens leading to complete destruction of the plant in no time. Killing fungus gnats are very crucial as this can become a serious pest problem leading to mass damage to your crops.
One way of killing these insects is by attaching yellow sticky traps which tend to attract these bugs especially the adult ones. Reduce organic debris and also the amount of moisture in the media as damp conditions promote growth faster.
You can kill these insects by using chemical products that are mostly organophosphate based. Common ones include acephate and malathion; make sure that you handle these products carefully and keep them under lock and key always.
Carbaryl is another chemical that can be used that is effective against eh gnat larvae too. For temporary purposes, you can use Pyrethrum or Pyrethrin containing products. All agricultural departments do not promote the use of these chemical products for hydroponic plants so make sure that you find out which ones are legal in your town or city.