Customer's SURF2 which can be seen in the third photo in the round circle in the sump area...
"Here is pictures of my Only SPS system in KUWAIT, My system is running without any refugiums, chaeto reactors, Biopellets or any NO3 reduction dosing.. but running only with Surf2 algae scrubber, and reactor for GFO (Rowa) and another for Carbon. Usually I leave Surf until it is full and starts to die and become yellow, then I take it out to the garden and wash it with fresh water with slightly high pressure so all dead algae falls out easily and the green one stays inside then I return it to the sump with 10% water change ... usually this happens every 2 to 3 weeks cuz my system is ULNS" -- Mohammad Abdullah in Kuwait...