A hot tub skimmer is supposed to sip the “floaties” (leaves, dandruff, hair, bugs, body oil, debris, etc.) from the water surface into a contained area. Hot tub skimmers have evolved over the years so its important to find what you need.
A well-engineered hot tub skimmer intentionally plans the contours and water currents to sweep the surface floaties into the surface skimmers. A poorly designed tub can have back-eddies that trap the floaties in the corners. This makes your water surface less clean and can create an oily/scummy ring around the tub where surface oil accumulates.