Here is a customer's old SURF2x in saltwater. This old model has the old light-frame which did not block the red light from getting out like the current models do. Light is the same though, pure red 660nm deep red, just like natural seaweed uses at the beach and reefs.
Some people ask why the inside of the SURF is white, which you can see with the algae pulled out in the second photo. The reason is because white reflects the red light back to the algae at the farthest point away from the light, which is where the light would be weakest. As opposed to a waterfall, where light travels mostly through air, the growth in a bubble upflow scrubber has to go through algae most of the way. So reflecting it back to the algae keeps it brighter, using the same wattage light.
The growth in this photo is almost all Cladphora. Add some vinegar and olive oil, and it's a great salad...