The flies will be rattling around a transparent cylinder of dimensions roughly 3" by 1". Three LEDs along opposing sides of the vials should be plenty. They can be placed within 1 cm or so of the vial wall.
The flies will be rattling around a transparent cylinder of dimensions roughly 3" by 1". Three LEDs along opposing sides of the vials should be plenty. They can be placed within 1 cm or so of the vial wall.