If you go the nematode route then you need to employ a couple other strategies. One is to cover the surface of your grow medium with either sand or clay Pebbles. I prefer clay Pebbles cuz you can take them off and reuse and whereas you can't do it with sand. If you do clay Pebbles you need to wash the heck out of them because they're very very alkaline. Anyway what the sand or the clay Pebbles will do is create a barrier so the Flyers can't get down in there to lay larvae in your medium.
The other thing is to let your plants go very dry before your next watering. Ideally you would do this in conjunction with putting Pebbles or something on top as a barrier and going with your nematodes or your mosquito bits. The idea would be to try and kill off as many as the buggers down in your medium as possible because they like things very wet.
You can safely take a cannabis plant to full Wilt before your water, just don't hit them with a bunch of nutrients when they're wilting just give them the water.
Then of course you can pick up some yellow sticky traps to hang in the tent and catch any fliers that'll help you monitor when you've got your problem solved. If you don't see any flyers for at least a week then I think you'll be okay.
Where I'm currently growing
Where I'll be Nov 1st