General Hydroponics CocoTek Mixed Bricks are an environmentally-friendly growing media that are pH balanced, contains low sodium content for coir fiber, and last up to 3 years. CocoTek Compressed bricks are composed of low-sodium coconut coir and chips. Each brick will expand to about 2.5 gallons when rehydrated with water. CocoTek Organic Growing Media is ready to use in a mixed brick (25% chips and 70% coir), or make your own blend by combining the Chip and Coir bricks. The Coir brick provides excellent water retention and the Chip brick improves aeration. A custom mixture of the two creates an ideal growing medium for a specific growing environment.