Self-Priming Hang-on Back Filter: Equipped with an auto-priming function, fishkeeper aquarium filter operates immediately upon power connection, eliminating manual water priming. The waterfall-style wide outlet enhances water circulation and oxygenation levels, ensuring optimal aquatic conditions Triple-Layer Filtration System: ① Removable bottom sponge for coarse debris filtration; ② Bio-ceramic quartz balls (included) to neutralize heavy metals and organic waste; ③ Replaceable Cartridge: Activated carbon core with dual-sided sponge effectively neutralizes odors and impurities Ultra-Quiet Operation (<30dB): Engineered with a low-noise rotor, the aquarium filter operates below 30 decibels, making it ideal for noise-sensitive environments such as bedrooms or offices without disrupting daily activities Anti-Intake Safety Design: The hidden cable design can secretly fix the wires to prevent wire wear; the water inlet adopts a small and fine hole design, which effectively prevents the danger of small fish and shrimp from being sucked in Easy Installation and Detach: No tools are required, and fish tank filter can be quickly installed and removed. Please note: The thickness of the fish tank for 3W is 0.625 inches, and the thickness of the fish tank for 4W is 0.75 inches fishkeeper Aquarium Filter 5-20 Gallon Power Quiet Hang On Back Aquarium Filter Multi-Stage Filtration Fish Tank Filter Waterfall Hob Filter for Freshwater Saltwater (4W 132GPH )