I am growing indoor hydroponic jalapeno peppers and have a problem
with mostly gnats. I need to reduce / eliminate the gnats hovering
over my potted plants.

I pot my plants in gallon pots filled with hydrocorn. I feed them
with drip feed irragtion spikes.

Would som D.E. thrown on top of the hydrocorn in the gallon pots
prevent these gnats from breeding in the clay pebbles? If so, which
kind of D.E. should be used? Horticultural or food grade?