I placed the Eheim Power Algae Scraper base unit in the handle, turned it on, and started to push it straight down the glass, from the top to bottom. It powered its way through the algae in a single pass. I had to keep it at about a 30 degree angle, and it only seemed to work on a downward stroke, not when dragged “backward”. The blade pivots so you have a little margin of error as you press the blade against the glass. As I scraped away several week’s worth of algae, I could not help but be impressed with how well the Eheim Power Scraper was working.