1.: Made of high-density foam sponge, it has better filtering effect and provides an environment for fish. A variety of sizes are available for greater versatility. 2. Enhanced filtration: These pre-filter sponges help capture particles and debris, extend the life of the filter media, provide efficient water flow, reduce clogging, and achieve long-lasting filtration. 3. Long-lasting and durable: Suitable for use as a quicksand filter. The sponge should be used to separate the internal media (such as quartz sand, etc.) from the bottom acrylic plate to extend the life of the equipment. 4. Ultra-thin design: The innovative ultra-thin design saves the internal space of the aquarium and is more beautiful. Please check the sponge regularly and replace it if it becomes thinner. 5. Wide range of applications: Suitable for shrimp tanks, fighting fish tanks, breeding tanks, goldfish, discus, guppies, fry, young fish or other fish. Suitable for your fish, suitable for freshwater and saltwater environments.