got bugs! help

I noticed that I have tiny flies in my prop, I have clones and seeds in there so need to get rid! I heard that a layer of sand on top of the soil would do the trick, is this true??? also I was told that ladybugs would get rid too???? not sure about that! any idea's please reply
thanks!!!

Tiny flies as in the dreaded FUNGUS GNATS??? Sand would work, but there are other, "better" ways also....Dryer soil. Hot shot pest strips, GoNats or other related gnat killers.

I put sand over all the tray in prop but with it being a prop I can't really let the soil dry out. I read somewhere that broken up chillis work is this true? I have put some in prop anyways coz the are really pissing me off!!