I've been noticing a lot of flies in my run (sand) since the weather has been warmer. I did some searches on here and came up with something called "Dry Stall" that people sprinkle in their runs and coops. I think it helps dry the poo quickly so it doesn't attract bugs. It's fairly inexpensive at $10-$15 for a 40 pound bag, but I can't find it with a reasonable shipping price, so I'm going to try and find it locally. I hope this helps and that it works!! Any other ideas would be great.
Thanks for the info, birdaholic. I'm going to try that tomorrow!