Ok...let me clear this up right now...your organic soil doesn't necessarily come with gnats...anytime you overwater you WILL get fungus gnats...Most gnats you see in houses that aren't around a bowl of fruit are fungus gnats...they come to wet towels and sponges, leaky faucets...anywhere there is a good bit of moisture...you can use coco, or rockwool or just DWC with hydroton and still get fungus gnats...they just like places where there is light, and lots of water...they are attracted to mildew and it's many associated fungi...they aren't there for the plants...they are there for the wetness of the soil...so if you don't overwater you will never see gnats, even if they came in the soil.