If they live in the soil, fly, and don't eat the plants, it's probably fungus gnats. I got them twice, and they're fairly easy to get rid of. Kill one and compare it to
some pix online. Just because they're not eating the plants doesn't make them safe to have around. Their larvae will eat the plant roots. First time I had them, I got lady bugs and nematodes; they went away after a few days. The second time I got them I only got the nematodes and they were gone within 48 hours.