Sciaridea?

lil far away in picture, but looks like a fngus gnat. These are very common. If the media you buy is stored outside, you are almosot guaranteed to bring them home from the store. BTi -- in north america the common product name is "mosquito bits" and there are also "mosquito dunks" that you can toss in a rain barrel or small water thingamabob in you yard. Baciluss Thugengenisis mawatchamacallit... lol.. as long as that's the active ingedient it'll be the same thing... misspelling it on google will give you the correct spelling. It kills them in larva stage only. Anyway, this is a great preemptive treatment. you can avoid the problem compeltely in future. It also woks well midstream infestation... it may take 2-3 weeks for it to have a majo impact on population. this along with sticky taps killing adults will take care of it faster. pyrethrins is a kill on contact product that supposedly biodegrades in 72 hours. i would not use this on flowers, of course, but vegetative plants is definitely fair game. This kills on contact... straight forward.. onyl adults but again in combination with bti will rid you of the infestation in 1-2 weeks. BTi is not pefect.. but at worst you'll se 1-2 gnats at at ime over the course of entire grow if you use it preemptively.. it'll never be wose than a couple.

I honestly don't know what they are by just looking at a picture.. so I'm going to base my answer on something you didn't tell us - what kind of damage did they do to your last grow? If they sucked on your leaves and left small white dots, they can easily be killed off with either Dr. Zymes Eliminator or some Spinosad... both are organic and can be used right up to day of harvest with no effect on the taste of your harvest. Just mix as directed and spray the tops and bottoms of all leaves just before lights out. This will kill the adults, eggs, larvae of any insect that sucks (as opposed to chews) on the leaves. If they damaged your roots, they're fungus gnats and those can be killed by using Mosquito Bits... just soak the granules as directed and use the water to water your plants. Fungus gnats like to live in moist, wet soil so if this is what you have, you are most likely watering your plants too much, keeping the soil too wet. Good luck!

Small black flying bugs, Since i had them against my last grow i sprayed with insecticide all the area before my new grow, And sterilized the terrain with boiling water, but they appeared again