let your soil dry up before watering. nats lay eggs in wet soil if it never gets dry the eggs hatch . you can let it dry , or put sand on top of the soil. another trick is leave a bucket of water out. the bugs fly into it and drown , very affective . best bet water them when the soil is dry on top. I use a cheap organic soil made for tomatoes. it costs 6 bucks for 20 gallon bag. and I bought soil from big lots. even cheaper no bugs. and cheap mj no bugs. its how you water. worst soil I have ever used was fox farms ocean forest it was like have my woman grabbing out 100 dollar bills. soil is soil. just add pearlite for drainage. if your soil does not dry up with in 2 or 3 days add pearlite 50/50 , mix you will never have any over watering problems again . just water every other or every day depending on your pot size