Fungas gnats or Blackflies?

iam 5 weeks into flower atm, and growing in coco as i went to water the girls today i noticed a few little black flying things on the bottom of one of my plants stem.
im pretty sure its gants iv been reading up, i saw maybe.....5-8 of the fuckers.
sucked a few up with the Vacuum :D also squished 2 ha u fuckerz!
anyway, i hope maybe i just cuaght em quick cus there is only a few but im assuming the might have layed eggs allready which might hatch in say 2 days from now.
i put sum paper plates over the tops of my pots to stop any more breeding in the soil.

im just wondering what is safe to use for a plant 3 weeks from harvest, its a nice grow atm dont want to ruin it. i got some yellow sticky traps up atm cuaght nothing so far.
i saw some stuff at my hydro store for gnats that u mix with ur feed and it kills eggs and larvea is this the best sollution?
and or diatomacious earth but unsure where sells this in the UK?

suggestions please

many thanks

just went through the same...I grow coco as well. A layer about 1 inch deep of fine play sand over the top of my coco ( pain to water, but the gnats can't crawl through the sand) yellow sticky traps...that should do it...I also used safer soap, but since your in flower I would cautiously use. Fortunately fungus gnats aren't that damaging, but annoying :)

Ye thing is i dont get paid till tomorow, so atm iv still got the pots covered with card so nothing can get in or out.
i got some alcahol spray i been taking my plants out every few hours and spraying around the card to repel em, i think it killed a few aswell.
hadnt seen many all day today maybe just 1-2 then just now i saw another 8 or so so i killed the lot lol
guna go get some play sand tomorow and some yellow, pest strips before they infest!!!!

Any reccomendations on watering whilst the sand is on? im guna wait another 2 days before i water again, its been 2 allready, i just wanna dry out the soil so when the sands is on they just suffocate quick time, when i do water again shall i water over the sand? or push the sand away and water the medium then recover with fresh sand?

Quick replys appreciated :)

It depends on watering... I grow in smart pots (fabric pots) so there is 2 ways I water when I use the sand...my bigger plants I just suck it up and top feed....takes a little bit longer as you have to wait for the water to filter through the sand...the other method I use (which is way quicker) is to drop my plants into a bucket of water with nutes...since I have fabric pots, the water soaks into the whole root base rather quickly.

It is a pain to water though...not going to lie, but this is a great solution that has worked great for me without using harsh pesticides. Since your pretty close to harvest It should't mess you up too bad.

yeh mate, i think il drill some holes in the sides of my pots and water em by soaking them in my nute mix,
getting sand tomoz, Cheers for ur help mate :D

Ok, So i bought some pre-washed child freindly play sand from my nearest DIY store.
i watered the ladies then covered the coca with about 1 1/2 inches of play sand and compressed it tight.
had to kill another bunch of the gnats whilst doing this.

How long do i leave the sand on for? i have 3 weeks left atm, just leave the sand on till the end?

cheers