window screen
I get nylon window screen, I cut big circles ( or other shape, depending on the pot shape ), then I cut a slit to the center, and a small hole in the center. I put this over the soil and cut off the excess so there is a fringe to tuck into the pot. Then I pile big round smooth "river rock" on the surface to keep it in place.
The rocks get taken out and washed about once a week; the screen too as needed. This also keeps gravid girls from secretly laying a clutch in a Schefflera.
Hope that helps.