The filter was taken apart and the outside of it was painted black. No paint on the inside - very important.
For the light, we cut a square piece out of the cover and glued in a small custom built acrylic cube on top. The outsides of both were also painted black. We wanted as little outside light as possible getting into the HOB/fuge. The light we wired was a single warm-white LED from RapidLED, along with a heatsink and standard driver. It was wired separately from the HOB's own pump because we wanted to be able to individually control it.