Black flea like bugs in soil

Hi can somebody please help me. I've found black little bugs the size of fleas in the soil and they fly. A friend told me it could be scarid fly and gave me some scarid fly drench. I put five litres of water into a bucket and 1ml of the drench and shared it around four plants. I did this three times. Do you feel this will kill them? The drench is really potent and I'm hoping I'm not going to kill my plants. I am in week four of flowering. Stressed!

i use play sand from walle world

Fungus fly. I usually use a layer of perlite or sand on top of soil to keep them from thriving in the soil.