They're probably fungus gnats. The little flies are the adult form. They hang around the surface of the medium most of the time where they live for about two weeks while breeding, laying eggs, and completing the fungus gnat life cycle. Those in the larval stage are tiny little worms that live in the potting medium.

The larvae mostly eat decaying bits of medium, but that does not necessarily mean your medium is rotted. In organic mediums, the decay process is already underway to some extent even as it comes out of the bag after you buy it, so the worms don't have to wait. The larvae also feed on the roots of at least some kinds of plants.

Fungus gnats multiply rapidly and can become a real nuisance to those growing orchids or potted plants. One control method is to hang yellow sticky cards around to catch the adults, but a much better solution is to kill the larvae. The most effective way to do that is with a bacterium called Bacillus thuringiensis subspecies israelensis.

It's easy to find and easy to use. Just go Lowe's, Home Depot, or a garden center and buy a pack of mosquito dunks. They have that bacterium in them because it's also effective against mosquito larvae. You can float one of the dunks in a bucket of water for a day or two and then draw from it to water the orchid. You can add more water to the bucket as needed. The dunk will still be good until it's gone.

You will start killing the larvae right away. Subsequent waterings will get those that hatch later. The bacterium is not dangerous to humans, animals, or plants.

Anglo - thank you so much. I will go buy it today and I 'll do it over the weekend. I was really afraid to spray something on my beloved plants. Thanks again