How to prevent fungus nats?

I have read before that keeping a layer of growstones or hydroton clay balls on top of the soil will promote root growth near the top of the soil and I was playing on trying this out my next grow but then I read that fungus nats thrive in warm moist environment in the top like 3 inches of the soil. Growstones will most likely cause fungus nats to grow right? If used in the way I mentioned before the layer of growstones on top of the soil

Put 2 inches of sand on top of your soil and bottom water. The gnats need moisture and the quick draining sand combined with bottom watering will kill off your gnats in about a week. 1 more week and the eggs are also dead.

If you need a quick effective solution then a drench with azamax would be a good choice.

I do not have this problem I wanted to start using grow stones on the top of my pots to keep the top layer moist and encourage root growth to the top soil but I also read that gnats thrive in conditions like I just mentioned so I was wondering if that would be a bad idea or not

Gnats thrive in moist soil. Topping with sand or small rocks should shade your soil too. If you're outdoors, use grass clippings