pests

hi ive just set up my 1st ever grow and i'm already having problems well its just 1 problem for now but anyway here it is ive got my seeds germinated and put them under my light im using a hydroponics system which is running nice ive got a 250 watt HPS light running and got some nutrients ready to use when they are 2 weeks old however my grow room is a back garden shed the temperature is fine but already ive noticed small flies in the room they arent so small that they are microscopic they are like a midgie size fly or green fly im just wondering if at this time of year they will be plant affecting pests or just predatory pests as an uneducated guess i would say most of the crop affecting pests would be in hybernation this late in the year but as this is my 1st grow i dont want to take any chances i appreciate any help and advice given and all comments are welcome even if its to diss me on my newbie uneducated approach i have my room coated in mylar and is as sealed in as an outdoor shed can be i have an intake and outake airflow syestem that has a webbing type film allowing air in/out but no bugs but the little ***** still find a way in (sorry for the ramble...)

They are fungus knats. Its from the medium being too moist. They feed on your roots. Ya want to kill them fast.

ok thanks for that

will it still affect my roots ieven though my plants are in hydroponics and they have no access to them? and what is the safest way to kill them and not harm my plants?

also would adding more air vents help eliminate moisture in the grow room or would that make it worse?