Posted: Fri Dec 12, 2008 2:10 pm
I recently had the same problem.
What I did was aim the filter output at the surface so there's a lot of current surface so they can't lay eggs. Also, the thing that really helped was good ol' fashion swatting. The first day there was a whole bunch of flies that I squashed, then a little bit less every day until they were basically gone.
As far as I know, they don't hurt your turtles.
Ralpheal, "The 'L' is silent."
Frankie, "Young at heart."