Did you pot your Gerbers in a commercial potting soil?

When you water the plants, do you see anything come to the surface of the soil?

Sounds like damp gnats. They won't hurt your plants, but they are a dreadful nuisance inside. You can get rid of them by topping off your pots with about a quarter inch of sand or pea gravel.

They sound like fungus gnats and the larvae which live in the soil do eat roots. They can be controlled with BT products either one marketed for gnats or mosquito dunks sold for mosquito larvae control. Al