Fungus gnats used to give me so many issues when I did Promix-HP with bottled nutes years ago. You don't have a lot of options to combat them in that growing style, and it's always moist and bare on top. I had clouds of them, and yellow sticky cards didn't really help too much with the population I had.
In organic we have a lot more options, and in no-till specifically we have even more options for control due to creating a stable environment cycle-after-cycle to build up predator populations. From predatory nematodes to mites, there are creatures you can either introduce or come with your fresh worm castings that will eventually keep everything more balanced. I haven't even seen a flier of any kind in my tent in the last several grow cycles, so I don't even monitor with yellow stickies anymore.
One main issue is that after the gnats are reduced, you still need something to feed your predatory mites and nematodes to keep them happy and growing so that the gnats do not re-establish themselves. Springtails are good for this because their larvae is also loved by these predators. Plus they aid in nutrient recycling on a scale that science is still trying to figure out completely. All we know so far is that their role in this is big and formerly under-appreciated. You'll see lots of springtails in fresh worm castings, so that's a good source for them.
I guess what I'm saying here is that use fresh homemade worm castings in your initial soil mix. Ensure it has diversity by adding the best garden soil from the root zone, along with a soil sample from as many environments as you can such as a forest. Put in in the worm bin with the high carbon material (paper, leaves, straw, etc.) and some nitrogenous regular food. In a couple months add that to your initial soil mix. You wont have to pay for predatory mites and nematodes. They're common, and everywhere. Plus you introduce a wide diversity of bacteria, fungi, protozoa, and other creatures to your worm bin that might survive to later end up in your grow soil.