Gnats?

There are some bugs flying around my plants at the moment. I first thought they were fruit flies crowding around, and didn't think much of it. After reading up a bit more on pests, I went to take a closer look at one of the bugs, and noticed it looks nearly exactly like a gnat. However, differences include: These things are all white except the black eyes and they are about the size of fruit flies.

Could anyone help me out here? I'm on my first grow at the moment and was thinking of using sand. If these really are gnats, how would I go about using the sand? Pour a layer on top, or what?

Thanks in advance!