Yes, the surface prefilter is the same thing as the surface skimmer. What is important with skimmers, more than the amount of water they flow, is the contact time that the water has with the bubbles. If you're forcing too much water through the skimmer, it goes through so fast that it doesn't shed the DOC
's onto the bubbles. The name of the game is to have the water molecules slam into as many bubbles as possible. One advantage to the Remoras is they use an air injector instead of a venturi. It's like holding a garden hose with a reducer over a bucket of water...the high speed water jet slamming into the water in the bucket makes tons of tiny bubbles.