Black Tsetse Bugs
I seem to get a lot of little black tsetse flies around my plants. How do I get rid of them?
These articles should help: https://www.gardeningknowhow.com/special/children/fungus-gnats.htm
Fungus gnats love wet soil. Try letting your plants dry a little between waterings. Between new soil, Bt and drier soil, you should get a handle on fungus gnats.