Help your finned friends breathe easily with Lee's Aquarium & Pets Original Under Gravel Aquarium Filter! This top-of-the-line biological filtration system is designed for use in both freshwater and saltwater environments. This durable unit draws water through gravel into specially designed plates that are made of high-quality plastic to resist splitting and cracking. It includes airline tubing， multiple plates， adjustable one-inch uplift tubes， a Discard-A-Stone air diffuser， and a fish-saver elbow.