Krylon acrylic fusion spray paint ( found in walmart ) has been used by MANY reefers over years without any traceable negative effects. I have friends who have acrylic overflow boxes that they painted with this paint, and their reefs are fine. Just make sure its dry and the paint has cured before you let it touch the water.
It sticks well to plastic, but if you're having troubles getting it to stick, just sand the overflow box a little ( you won't see the scratches it once it's painted )
Edited by Pete Moss - March 04 2013 at 8:06am