little black flies

Hi everyone, I am new here. I have bought myself a greenhouse. Have put some seeds in Tomatoes, onions carrots etc. Little black flies have been appearing, any idea what they are and how do I get rid of them please.

 

Hi gloria welcome to the forum sounds like fungus gnats their lava infest the top layer of compost and will eat the roots of seedlings,try to keep the top layer of compost dry(they love it damp)water from the bottom cover the top of the compost with sand it keeps them out you can get biological control from here but it will only work once it gets warmer
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Hi Gloria and welcome to GC.

 

Hi Gloria and welcome to GC from me too.

 

Hi Gloria, welcome to GC, I'm new too!

 

Welcome to you Gloria