This is a low-power mode of the SURF4x. It is a pattern of 6 of the 12 LEDs, connected to one of the power cords. The other 6 LEDs are connected to the other power cord, and when both are plugged in you have full power. Low-power lighting (combined with shading from the included black shade cloth) is usually needed on new installations because the bright red light is reflected off of the white Green Grabber® rocks and strings, making the light even brighter; too bright for algae to grow. Once growth occurs, however, you need the bright light to travel through the growth to keep it alive and growing.

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And here are the printed instructions if you want to read more:
https://algaescrubber.net/SURF-Instructions.pdf